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Impacts of Rotation of Moon

08/21/2017 5:20 PM

As I never studied Astrophysics during University years, I am asking the following from a naive standpoint. After watching the "great" [TIC] solar eclipse of 2017, I started wondering about a few facts about the moon:

I understand the observable face of the moon is directed towards us continually, so I assume the unobserved face would be generally be directed towards the sun and would be very hot given there is minimal atmosphere.

I also wondered what different impacts the moon's rotation has on the earth.

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#1

Re: Impacts of Rotation of Moon

08/21/2017 5:30 PM

Everything is always moving....The moon affects the gravitation pull on the Earth's surface, the tides are one effect...

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#13
In reply to #1

Re: Impacts of Rotation of Moon

08/22/2017 3:35 AM

Looks odd viewing more from the south.

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#100
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Re: Impacts of Rotation of Moon

08/26/2017 2:34 AM

Dear Mr. SolaEagle,

I observe a difference in the animation of moon orbiting the earth. The difference is the plane of orbit of moon appears perpendicular to the axis of earth (axis for self-rotation of earth)

Actually, what I read is, the Moon's plane of orbit is inclined by 27 Deg. (or 23 Degrees) to the axis of earth's self rotation.

I am eager to know from you more.

Thanks,

DHAYANANDHAN.S

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#109
In reply to #100

Re: Impacts of Rotation of Moon

08/28/2017 9:22 AM

I think you are correct, sir. Good answer!

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#2

Re: Impacts of Rotation of Moon

08/21/2017 5:40 PM

Give or take the minute difference occurring during a lunar eclipse, every part of the surface of the moon (at the same lunar latitude) receives equal insolation.

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#7
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Re: Impacts of Rotation of Moon

08/21/2017 8:54 PM

Well, the poles of course get less insolation than the Moon's equator, but yes, the moon rotates on its axis once a month, so there is no permanent 'dark side'.

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#3

Re: Impacts of Rotation of Moon

08/21/2017 5:43 PM

Then you got yer werewolf's...

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#4
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Re: Impacts of Rotation of Moon

08/21/2017 5:54 PM

Where?

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#5
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Re: Impacts of Rotation of Moon

08/21/2017 6:15 PM

London,of course!

Aaoooooo!
Werewolves of London!
Aaoooooo! (Repeat)

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#38
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Re: Impacts of Rotation of Moon

08/23/2017 7:40 AM

There, there wolf!

Why are you talking like that?

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#10
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Re: Impacts of Rotation of Moon

08/22/2017 3:01 AM

werewolf's werewolves

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#12
In reply to #10

Re: Impacts of Rotation of Moon

08/22/2017 3:32 AM

Cryptobiology is adequately described cryptogrammatically.

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#16
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Re: Impacts of Rotation of Moon

08/22/2017 10:25 AM

How do you know he did not intend to use the possessive singular?

The werewolf's "X"? His "je ne sais quoi"? The werewolf's effect on the earth's rotation? I don't know...

I will say, the length of the solar day on the moon does present some rather interesting possibilities for heat engines to operate there, but the upper temperature might have to be pretty high indeed, as the low temperature would have to be somewhat elevated for an effective radiative heat exchanger to operate. Now solar PV arrays will also work, just not so great when the nights are that long. Lunar orbiting solar arrays are very appealing, since they can be set up in a luna-stationary orbit, and microwave the energy back to surface in line of sight.

The heat engine concepts would probably all relate back to various Stirling oscillator engines, but once again, there might need to be vastly larger radiative heat sinks, coupled back to the primary engine by circulating coolant that does not freeze in lunar night conditions.

There you go: What an interesting thought experiment for some bright, young minds to work on!

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#15
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Re: Impacts of Rotation of Moon

08/22/2017 10:18 AM

Now put that thing away, that is for nap time.

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#6

Re: Impacts of Rotation of Moon

08/21/2017 8:50 PM

NOVA, Discovery Channel or similar has an hour long special on "What if there were no moon?" (or similar title). It is amazing and a little scary.

To begin with a lot of people that are much smarter than me believe that at least part of the moon used to be part of the earth. After a crash much bigger than your average I-4 Orlando crash a big chunk of earth rock was blasted out and became part of the near side of the moon. The important part of that story is that the moon is heavier on the near side than it is on the far side. That, combined with the centrifugal force equation being in the sweet spot keeps the same side pointed toward us all the time. It wasn't always that way and it won't always be that way.

The moon causes the ocean tides and also has caused the earth to not be round. No, the earth is not flat. I don't recall exact numbers but the earth's diameter from center to equator is several miles more than the diameter from center to pole.

The moon gives our orbit more stability than we would have without it. Like eating fruits and grain products? The moon helps give stability to our seasons. Impacts with the earth would have a greater chance of giving our orbit wobble without the moon.

Somehow the sea turtles know about the full moon and time their hatching. Little turtles break out of their eggs and run toward the moonlight shimmering on the ocean.

If it wasn't for the moon we wouldn't have werewolves. Think of all the movies we would have lost. Think of all the moonlight activities you would also have lost.

I don't recall the exact details but some scientists say that we wouldn't be here without a moon and the big crash that caused the uneven density. The liquid core of the earth is believed to be necessary to have earth's magnetic field. The magnetic field is needed to help shield us and all life from solar radiation. It also helps to shield our atmosphere from the solar wind. Apparently it is considered to be very difficult to create life before a planet cools down to the point that the shielding magnetic field is lost. The friction from the big hit warmed our core to give us extra millions (billions?) of years of magnetic shielding. But the blast did not fully reset the clock on the processes to form life. Thus we had a much wider window to form life than we would without the big crash. That isn't a "thank you moon" statement but it is a "thank you event that keeps the same side of the moon facing us" statement.

Here is the part that is not fun. The energy required to make the tides flow is dragging down the total kinetic energy of the moon. Because of that the moon is constantly getting farther away from the earth. I don't recall the exact number. I think it might be in the neighborhood of half an inch a year. There will come a day when the uneven density of the moon will no longer nudge the centrifugal force equation and we will see different sides of the moon from the earth. Later the moon will drift farther and farther away until it no longer stabilizes our spin. We will be at risk of weird seasons and disrupted agriculture. The big question is whether Congress will pass budget and health care bills before then. My guess is that they won't.

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#9
In reply to #6

Re: Impacts of Rotation of Moon

08/22/2017 12:20 AM

Hmmm, you either aren't recalling correctly at least some of what the NOVA, Discovery Channel or similar show said, or the show was wrong about some things.

Going in reverse order:

The last paragraph, 'Here is the part that is not fun', is all kinds of hosed up.

The tides are not `dragging down the total kinetic energy of the Moon`. To the contrary, kinetic energy is being transfered to the moon. As noted the moon is getting farther away. How could that be if energy were being taken from the Moon?

The tides are slowing the day on Earth and adding kinetic energy to the moon as the 24 hour period of the Earth day attempts to make thr 28 day period of the Moon catch up.

I'm also quite suspicious of the lopsided moon hypothesis presented as fact. Density difference is not required for tidal locking. In fact, density difference really shouldn't cause tidal locking. Remember things of the same mass in space fall at the same speed regardless of density. Also, in orbit, there is a ballance between gravitational attraction and inertia, so more mass or greater density will have just as much force opposing as attracting in a circular orbit.

Also, why would the tidal lock be undone without outside interference? AFAIK, the tidal lock can be expected to continue. Eventually the Earth would also tidally lock with the Moon as the Moon's orbit and Earth's day eventually synchronize...though the sun is expected to expand to large than the Earth's orbit before that would happen.

.

Okay, just a question here... are there no sea turtle nests on north facing beaches in the northern hemisphere nor on south facing beaches in the southern hemisphere? ..or are there always steep enough waves to reflect the moonlight back?

.

What about this wobble? Seems that we have wobble now. How could more wobble be possible without a satellite?

.

The oblateness of the Earth is due to its own rotation about its axis. The effect of the gravitation of a satellite such as the Moon would be to make things more prolate, and to the extent of the tides it does, but this isn't the cause of the equitorial distance from the surface to the center being greater than that at the poles. The moon is somewhat prolate.

.

I hope you take this as intended, not a personal attack on you, just a challenge to the veracity of the information posted.

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#26
In reply to #9

Re: Impacts of Rotation of Moon

08/22/2017 4:00 PM

You say

The tides are not `dragging down the total kinetic energy of the Moon`. To the contrary, kinetic energy is being transferred to the moon. As noted the moon is getting farther away. How could that be if energy were being taken from the Moon?

No - as the moon gets further away its (linear) velocity and kinetic energy fall.

V2/R = Mearth*G/R2, V = √(Mearth*G/R). Its gravitational potential energy increases, can't remember offhand whether the two just balance.

And "What about this wobble? Seems that we have wobble now. How could more wobble be possible without a satellite?"

I believe it's accepted by astronomers that without a relatively massive moon the earth's rotation would be much less stable. It's one of several fortunate coincidences that helped the evolvement of advanced life on earth.

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#27
In reply to #26

Re: Impacts of Rotation of Moon

08/22/2017 4:08 PM

Interesting and poignant displays of your grasp of the subject.

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#29
In reply to #26

Re: Impacts of Rotation of Moon

08/22/2017 7:12 PM

Come on.

Are you really suggesting that to boost a satellite to a higher orbit, that you need to remove energy? Ridiculous.

If you take energy away from a satellite in stabke orbit, does it move closer or further from the mass it orbits? Closer. Duh.

.

The Earth is spinning faster than the moon orbits and they turn the same direction. How could the tides possibly be taking energy away from the Moon? Doesn't happen.

.

Gravotational attraction causes the tides to bulge nearest and farthest from the Moon (and Sun), yet because the Earth spins, drag with the Earth ofsets the tides in the direction of spin. This causes a shift in mass that leads the direction of travel for the Moon. This adds kinetic energy. Yes this shifts the orbit out trading some kinetic for potential, and since the orbit is of greater length, it takes more time, but that isn't the same as having less energy.

.

Come on, this is not difficult stuff. You may have been told the Moon drags the tides around, and from a certain frame ot reference that isn't necessarily wrong, but if it confuses you forget that idea.

The tides are dragging the moon around.

.

"...I believe it's accepted by astronomers that without a relatively massive moon the earth's rotation would be much less stable. It's one of several fortunate coincidences that helped the evolvement of advanced life on earth...."

.

That doesn't actually say anything. How are you defining stable? There seems to be no correlation in our solar system between having satellites and axial tilt of a planet, for example.

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#40
In reply to #29

Re: Impacts of Rotation of Moon

08/23/2017 7:52 AM

Are you really suggesting that to boost a satellite to a higher orbit, that you need to remove energy? Ridiculous.

If you want to boost a satellite to a higher orbit you fire a rocket at right angles to the orbit to push it vertically up. It then finishes up in a higher orbit, but at a lower velocity, determined by the equation I posted in #26. If you apply a force along the orbit, it ends up at a higher velocity but at a lower orbit, determined by same equation.

If you take energy away from a satellite in stable orbit, does it move closer or further from the mass it orbits? Closer. Duh.

So how do you account for the observation that the moon is receding from the earth? Measured by lasers at about 40mm per year according to my data.

Part of the energy dissipated by tidal friction comes from slowing earth’s rotation speed, part by slowing the moon’s velocity. Irrespective of whether earth’s rotates faster or slower than moon’s cycle.

That doesn't actually say anything. How are you defining stable? There seems to be no correlation in our solar system between having satellites and axial tilt of a planet, for example.

It says quite a lot. Axial tilt isn’t the issue, as you say it varies between the planets. Earth’s axis of rotation is about 67° from the orbital plain, that’s what causes the seasons. But helped by the relatively massive moon, it’s pretty stable at that angle. I haven’t read up on the precise mechanism how a massive moon helps, but do you know more about it than the astronomy experts?

Even if you didn’t understand this, there’s no need to resort to rudeness.

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#47
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Re: Impacts of Rotation of Moon

08/23/2017 9:19 AM

..."to a higher orbit you fire a rocket at right angles to the orbit to push it vertically up."

Really? Then why are the primary thrusters (not the yaw controls) always at the rear?

Actual velocity has to increase to move the craft to higher orbit. Let's not confuse orbital velocity, and angular speed, or orbital period, please. Yes, potential energy has increased, obviously, and yes kinetic energy has also increased. Orbital velocity< earth well escape velocity. Plain and simple.

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#54
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Re: Impacts of Rotation of Moon

08/23/2017 9:57 AM

Now this is getting interesting. Your comment brings out the difference between the Relativity/Analog and Quanta/Digital theories. With Relativity/Analog, you can make smooth transitions. With Quanta/Digital, you go for the "Quantum Leap"

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#58
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Re: Impacts of Rotation of Moon

08/23/2017 10:18 AM

Let's not confuse what goes on at the quantum universal scale with what takes place at the macroscopic, or classical universal scale. There really is very little analogous to compare. Energy in the macro world does not cause one to take quantum leaps, only leaps of faith. It is a leap of faith to go from a scale model of a machine to a 500 MW version of the "same" machine, and in fact it is never the same "scaled-up" machine.

All manner of things have to be added the larger it gets. Trust me on that, will you?

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#62
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Re: Impacts of Rotation of Moon

08/23/2017 11:57 AM

If you cannot scale-up the quantum universe, then how can anyone call it "fundamental"? I guess there must be multi-verses, because that just doesn't work in this one.

I didn't say anything caused a quantum leap. I just said that there are two ways to enlargen your orbit. Which one do you prefer?

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#64
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Re: Impacts of Rotation of Moon

08/23/2017 12:11 PM

It is scaled up through what is called statistical mechanics. I will not bore you with any serious mention of that right now. Some quantum phenomena are directly observable such as the photoelectric effect, emission of line spectra by atoms and ions, even band spectra of molecules are quantized, not just in electronic states, but in vibration and angular momentum (rotational) states.

Some nuclear quantum phenomena are also directly observable, such as gamma radiation photon by a decaying nucleus, etc.

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#59
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Re: Impacts of Rotation of Moon

08/23/2017 10:29 AM

Yes, really! Location of the thrusters on the craft is neither here nor there. If you want to go to a higher orbit, you steer the craft, presumably using 2ndary thrusters, so it points vertically up, then start the primary thrusters. If you want to go faster, in a lower orbit, you steer tangential to the orbit, then give it some.

Actual velocity has to increase to move the craft to higher orbit. No! V and R are linked by the equations below. R of course is height from the centre of the earth. Bigger R, smaller V.

V2/R = Mearth*G/R2, V = √(Mearth*G/R).

Maximum orbital velocity is when R = Re, radius of earth (or slightly higher) so = √(Mearth*G/Re). Escape velocity = √(2*Mearth*G/Re) ~ 11200m/s. Not sure what the relevance of that is, but I thought I'd throw it in!

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#80
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Re: Impacts of Rotation of Moon

08/23/2017 4:35 PM

The part you are ignoring or overlooking is that the added kinetic energy is converted to gravitational potential energy as it moves higher.

Satellites are moved into orbit and to higher orbits aboard launch vehicles which do not just point straight up and fire.

If you are in a stable orbit and you thrust straight away from the Earths center of gravity all you do is make the orbit eliptical, you don't move to a higher orbit. The thrust that matters is tangential.

You seriously think you can get satellites into geosynchronous orbit from LEO by removing kinetic energy?

Step back, reevaluate. You are going to see this and then you can recant your physics heresy, lest impressionable youth happen upon your uncorrected blunder and never fully recover.

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#106
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Re: Impacts of Rotation of Moon

08/28/2017 3:17 AM

Careful with saying "removing kinetic energy".

While "removing" is out of question due to preservation of Energy, there is a potential that the moon has indeed less kinetic energy as it moves away from Earth due to the increase in potential energy.

As a matter of fact the kinetic energy of a rocket decreases as it gains height.

So that part is certainly not wrong. But it is not the builder of the rocket that takes the kinetic energy out, it is the gravity field that transforms it into a potential.

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#108
In reply to #106

Re: Impacts of Rotation of Moon

08/28/2017 5:33 AM

I don't agree with your prohibition on stating kinetic energy is removed....and reading the remainder of your comment, it doesn't seem like you do either.

Kinetic energy is being removed from the Earth as it is transferred to the Moon, via the tides and the kinetic energy transferred to the Moon is converted into gravitational potential energy as it moves further out of the gravity well.

The preceding sentence has two solid examples of kinetic energy being taken away (or removed).

In the first it is transferred and in the second it is converted. In both cases the kinetic energy that formerly was in an object is no longer there from the same frame of reference.

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#118
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Re: Impacts of Rotation of Moon

08/28/2017 11:19 AM

"As a matter of fact the kinetic energy of a rocket decreases as it gains height."

That is only true after the fuel stops burning, or is throttled down considerably. As long as the vertical component of the thrust of the rocket is equal to or greater than the weight of the rocket at the current altitude, the rocket will be gaining potential energy, and all of the horizontal component of the thrust will be adding kinetic energy.

Once the fuel is not burning, it is effectively no longer a rocket, but just a projectile. At that point and beyond, your statement is correct.

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#72
In reply to #47

Re: Impacts of Rotation of Moon

08/23/2017 3:22 PM

Think about the definition of "orbit".

If you move a satellite to a higher orbit and increase it's velocity, it will no longer be in orbit.

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#74
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Re: Impacts of Rotation of Moon

08/23/2017 3:36 PM

OK, I surrender already, white flag and all, cease fire, please.

If one perturbs an object in a given orbit to a lower radius temporarily ( by adding kinetic energy by reaction impulse), the net result is the final orbit of the object will be higher potential energy (check), higher radius (check), and lower velocity and angular velocity (check). Am I now in compliance with the consensus opinion?

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#82
In reply to #74

Re: Impacts of Rotation of Moon

08/23/2017 4:45 PM

And there inlies the pitfall of consensus.

An utterly incorrect argument can gain support from those who previously had it correct, merely by ganging up.

.

Seriouly, please reevaluate. The Earth rotation and Moon orbit are very similar in direction. The Earth is turning much faster. Angular momentum must be conserved. The tides are attempting to pull the moon around faster, adding kinetic energy, which moves the Moon to a higher orbit as that kinetic energy is converted to gravitational potential energy.

When satellites in low orbit experience friction from the atmosphere, kinetic energy is removed, this does not cause the satellites to move further away as they slow. Come on! Wake up! You guys are smarter than this.

.

This is beginning to be a little disheartening.

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#84
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Re: Impacts of Rotation of Moon

08/23/2017 4:58 PM

It is indeed, sir. I even have a cousin that worked at NASA, shame on me.

I no longer have guns to stick to, and stones did hurt when taken away.

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#89
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Re: Impacts of Rotation of Moon

08/24/2017 9:07 AM

I defer to Kepler:

In astronomy, Kepler's laws of planetary motion are three scientific laws describing the motion of planets around the Sun.

Figure 1: Illustration of Kepler's three laws with two planetary orbits.
(1) The orbits are ellipses, with focal points ƒ1 and ƒ2for the first planet and ƒ1 and ƒ3 for the second planet. The Sun is placed in focal point ƒ1.
(2) The two shaded sectors A1 and A2 have the same surface area and the time for planet 1 to cover segment A1 is equal to the time to cover segment A2.
(3) The total orbit times for planet 1 and planet 2 have a ratio a13/2 : a23/2.

Astrodynamics

Orbital mechanics

Equations

[hide]

Efficiency measures

[show]

  1. The orbit of a planet is an ellipse with the Sun at one of the two foci.
  2. A line segment joining a planet and the Sun sweeps out equal areas during equal intervals of time.[1]
  3. The square of the orbital period of a planet is proportional to the cube of the semi-major axis of its orbit.

Tsiolkovsky rocket equation:

any such maneuver (or journey involving a sequence of such maneuvers):

{\displaystyle \Delta v=v_{\text{e}}\ln {\frac {m_{0}}{m_{f}}}}

Common misconceptions[edit]

When viewed as a variable-mass system, a rocket cannot be directly analyzed with Newton's second law of motion because the law is valid for constant-mass systems only.

All of this is from the Wikipedia page on Keplers laws.

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#90
In reply to #89

Re: Impacts of Rotation of Moon

08/24/2017 9:27 AM

Sorry about the way the equation turned out on the page. I encourage the reader to navigate to the links, and see it for themselves.

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#83
In reply to #74

Re: Impacts of Rotation of Moon

08/23/2017 4:55 PM

Oh, you give up too easily. The thing you're missing here is that the addition of energy doesn't have to manifest itself in the form of velocity (kinetic energy). Remember that a higher orbit not only has a weaker gravity, but also has a higher potential energy. If you can convert some of your present velocity into potential energy, then you can achieve a higher orbit without increasing velocity. The trick here is to leave one equilibrium, and achieve another. The point here, is that to reach that new equilibrium, it will require SOME FORM of energy (that can be turned into potential energy); In that regard, you were right. It just doesn't have to be in the form of velocity (kinetic energy)

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#79
In reply to #72

Re: Impacts of Rotation of Moon

08/23/2017 4:34 PM

You're quite right. However, to change orbit you have to leave the present orbit. When you get to the new orbit, you can adjust your velocity again. The trick here is to leave one equilibrium to achieve a different one. And that applies to either a larger or smaller orbit.

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#81
In reply to #72

Re: Impacts of Rotation of Moon

08/23/2017 4:38 PM

This is where your confusion lies. You don't move to a higher orbit and increase velocity. Increasing velocity moves it to a higher orbit and in doing so converts some kinetic energy to gravitational potential energy.

.

This is very very basic stuff. How are so many getting this so utterly wrong?

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#87
In reply to #72

Re: Impacts of Rotation of Moon

08/23/2017 6:27 PM

That's right, you can't choose velocity AND radius of an orbit. When one is specified, the other is determined, they're linked by the equation I posted earlier.

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#88
In reply to #87

Re: Impacts of Rotation of Moon

08/23/2017 11:36 PM

This we wholely agree upon. The equations are correct. Velocity and radius of orbit are indeed linked.

This absolutely does not indicate that energy is being taken away from the Moon, or that orbits with larger radii and thus longer periods are at lower energy than those of smaller radii and thus shorter periods.

The Moon is moving away, not because energy is being taken, but because energy is being transfered to the Moon.

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#94
In reply to #88

Re: Impacts of Rotation of Moon

08/25/2017 6:57 AM

Yes, you’re right in that and your earlier statements. Profuse apologies and humble pie consumed!

I see now that applying thrust (tangentially!) increases orbital radius. Decreasing velocity so lower KE but PE increased by 2x KE loss.

So as you say the moon is gaining energy as it recedes.

I checked the rotational KE of earth and KE of the moon, and somewhat to my surprise earth is about 7x higher, so there’s some available. That’s taking earth as uniform density throughout, giving high figure, but not by that much. I'd have guessed the moon being further away it would have higher KE, but there you are.

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#95
In reply to #94

Re: Impacts of Rotation of Moon

08/25/2017 11:17 AM

Admitting an earlier mistake and stating the correction goes a long way in my book. Kudos.

Everyone makes mistakes, it's what we do after that is more important.

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#96
In reply to #94

Re: Impacts of Rotation of Moon

08/25/2017 12:14 PM

Also, you raise an interesting point. Without interference of outside forces, eergy would continue to be transferred from the Earth to the Moon until the length of the (Earth's) day and the Moon's orbital period were equal. Essentially lifting the Moon to higher orbits while shifting geosynchronous orbit higher at a slightly faster pace until the two eventually meet.

Seems like a cosmic transmission when considering the tangential speeds involved as things progress, with energy being transferred away from the slower moving Earth to the faster (tangential speed not angular) Moon.

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#76
In reply to #40

Re: Impacts of Rotation of Moon

08/23/2017 4:09 PM

"...If you apply a force along the orbit, it ends up at a higher velocity but at a lower orbit, determined by same equation..."

.

Absolutely not.

Come on, think this through. If you have two masses in similar orbits, and you increase the speed of one and reduce the speed of the other, how could you possibly believe that the one with increased velocity will fall lower?

Same gravitational attraction;

As an object with greater velocity passes, will the path have a large or smaller radius than that of an object with less velocity passing at the same distance?

Move velocity causes less curvature which moves the object farther out and in doing so trades some kinetic for gravitational potential energy.

Less velocity leads to greater curvature as the object falls closer, some gravotational potential is traded for kinetic and the object experiences am increase in speed.

.

Your conjecture fails on several fronts.

Let's look at a huge fundamental problem: the Earth spins and Moon orbits the same direction, you propose that both are being slowed by the mutual interaction. Alarm bells should be ringing in your head. No?

Conservation of momentum is profoundly fundamental. You cannot have a system of two objects that mutually interact in a way that results in a net change in momentum, whether that momentum is linear or angular.

.

Just ask yourself what happens when satellites in LEO feel drag from the atmosphere. Does this cause them to move to higher orbits? Is that what happened to Skylab?

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#44
In reply to #29

Re: Impacts of Rotation of Moon

08/23/2017 9:04 AM

As I have been led to believe, the tidal interaction with the lunar spin, has resulted in a sort of "phase lock", slowing down the rotation of the moon until it is locked with orbital rotation rate, is that correct?

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#77
In reply to #44

Re: Impacts of Rotation of Moon

08/23/2017 4:16 PM

Tidal effects on the Moon (in the crust) are what caused it to become tidally locked.

The attraction of the Earth causes the moon to distort to a prolate spheroid. Before becoming tidally locked, as the Moon rotated with respect to the Earth, friction in the crust caused this prolate distortion to lag as the rotation turned it away. This effect slowed rotation with respect to Earth until it because tidally locked.

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#32
In reply to #26

Re: Impacts of Rotation of Moon

08/22/2017 11:10 PM

Energy is not taken away from the moon. Energy is transferred. So the moon orbital velocity increases making the moon move further away, while the Earth slows down. Total energy is still conserved.

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#34
In reply to #26

Re: Impacts of Rotation of Moon

08/22/2017 11:34 PM

Wait a minute. Kinetic energy is a function of velocity, and velocity is a vector. Therefore kinetic energy is also a vector. The potential/kinetic energy relationship with gravity is in-line with the gravitational pull. The kinetic energy as related to the orbit is perpendicular to the gravitational pull. Don't confuse one vector with the other.

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#41
In reply to #34

Re: Impacts of Rotation of Moon

08/23/2017 7:59 AM

Kinetic energy (or any other kind) is not a vector. Please see my #40.

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#42
In reply to #41

Re: Impacts of Rotation of Moon

08/23/2017 8:29 AM

Oh, but it is. As an object orbits something, it is constantly changing direction. Therefore its kinetic energy is constantly changing. What's escape velocity? it's kinetic energy AWAY from the source of gravity. If was was in the same direction as the source of gravity, it would NOT escape, but instead collide. If the direction of the kinetic energy was irrelevant, then there would never be any relative motion, collisions of any type, or the Centrifugal/Centripetal force phenomenon. The only reason that Centrifugal/Centripetal force phenomenon can work, is because of the vectoral property of the kinetic energy.

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#43
In reply to #42

Re: Impacts of Rotation of Moon

08/23/2017 8:56 AM

Some of what you say may be correct, but mathematically and physically energy is not a vector, believe me. Kinetic energies don't follow vector algebra rules, eg addition component-wise, let alone dot- and cross-products. Because velocity and momentum, both ordinary and angular are vectors it doesn't follow that energy is one.

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#49
In reply to #43

Re: Impacts of Rotation of Moon

08/23/2017 9:22 AM

Be careful what you say about momentum, it most definitely is a vector quantity, especially in quantum physics/chemistry.

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#50
In reply to #49

Re: Impacts of Rotation of Moon

08/23/2017 9:34 AM

Yes - momentum is (in simple terms) mass x velocity, while kinetic energy is mass x velocity2 - hence only one of them is a vector quantity.

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#52
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Re: Impacts of Rotation of Moon

08/23/2017 9:43 AM

Velocity is the vector ingredient. Since velocity is in both formulas, then both momentum and kinetic energy have vector components to them. Velocity squared makes that component even more emphasized.

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#55
In reply to #52

Re: Impacts of Rotation of Moon

08/23/2017 10:01 AM

Multiplying a vector by a vector (assuming a dot product) yields a scalar quantity. The cross product of a vector with itself is zero. Which you going to choose?

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#61
In reply to #55

Re: Impacts of Rotation of Moon

08/23/2017 11:34 AM

Velocity is a vector. Are you saying that if you square a velocity (The cross product of a vector with itself is zero), you'll always get zero? That doesn't sound right. Even vectors can be placed on a scale. What kind of scale or you talking about? There are many kinds of those, too. How does being a scalar quantity eliminate vectors? And what's a "dot product"? Never heard of one.

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#63
In reply to #61

Re: Impacts of Rotation of Moon

08/23/2017 12:06 PM

The dot or scalar product of 2 vectors A and B is a scalar, defined as A*B*cos(θ) where A and B are the magnitudes and θ is the angle between them. So if they are perpendicular, dot product = 0. If they're parallel, it = A*B. The dot product of a vector A with itself = A2.

Also if the components are Ax, Ay, Az and Bx, By, Bz, it can be shown that the dot product = Ax*Bx, + Ay*By + Az*Bz. This is useful if you know the vector components and need to find the angle between them.

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#65
In reply to #63

Re: Impacts of Rotation of Moon

08/23/2017 12:47 PM

Okay, I can sorta grasp that. But what about in the case of parallel but opposite directions? Especially when dealing with kinetic energy? if two identical masses are traveling in tandem, there is no conflict and the energies can be added. But if one is opposite to the other, they are still parallel, but there will be a collision. I still have a problem with believing that kinetic energy is not a vector. Direction/relative-direction makes all the difference in how that kinetic energy can manifest/affect/influence things around it.

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#68
In reply to #65

Re: Impacts of Rotation of Moon

08/23/2017 1:19 PM

You're confusing energy and momentum. Consider a head-on collision between two billiard balls, each with the same speed. Let's assume they don't rebound, so both come to rest. Total momentum is zero, and energy appears to be zero - but there was a noise and a bit of heat and maybe a bit of deformation (all of which is where the energy went).

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#69
In reply to #68

Re: Impacts of Rotation of Moon

08/23/2017 2:00 PM

Exactly, I was about to say something similar. Two equal and opposite vectors sum to zero, but if 2 bodies collide from opposite directions the energy is the sum of the two.

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#70
In reply to #68

Re: Impacts of Rotation of Moon

08/23/2017 2:07 PM

Okay, I can understand that. Kinetic energy changed its form to heat & noise energy, which is no longer contained in the billiard balls. It's now contained in the sound waves (which have momentum and direction) and the heat (which probably does not have momentum or direction). But how can you detach the kinetic from the momentum? Without the kinetic, there is no momentum. And vice-versa, without the momentum, there is no kinetic. When you detach one from the other, it has to change form and then it's no longer kinetic energy. That's how kinetic energy changes to potential energy. As it loses its momentum (vector) it also loses its kinetic energy. How can kinetic energy exist without a vectoral component?

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#73
In reply to #70

Re: Impacts of Rotation of Moon

08/23/2017 3:27 PM

How do you know the sound has momentum and direction? Are billiard balls directional microphones, I don't think so. Heat and sound both travel within 4π steradians from the zone or point of origin. Now, it is possible that for collisions of real objects the propagation of waves including heat and sound or other energies such as X-rays may not propagate with complete uniformity due to the residual of the (original) objects as such, which may act as absorbers or reflectors of said energy.

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#85
In reply to #73

Re: Impacts of Rotation of Moon

08/23/2017 5:01 PM

Oh, come on!! If sound had no direction, there would be no such thing as the speed of sound or the Doppler effect. And if it had no momentum, then it couldn't transfer its energy to your ear drums. Speaking of ears, what's between yours?

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#66
In reply to #61

Re: Impacts of Rotation of Moon

08/23/2017 12:57 PM

The cross product of any two parallel vectors is zero.

You can't just "multiply two vectors" without stating whether it's a dot product (yielding a scalar) or a cross product (yielding a vector or zero).

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#53
In reply to #49

Re: Impacts of Rotation of Moon

08/23/2017 9:56 AM

Yes, that's what I said. What's the point you're making?

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#57
In reply to #53

Re: Impacts of Rotation of Moon

08/23/2017 10:15 AM

Sorry, I misread what you stated about velocity and momentum. I guess I am in fact getting old.

Good job, by the way, keep up the good work, and sticking to your correct guns.

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#60
In reply to #57

Re: Impacts of Rotation of Moon

08/23/2017 11:09 AM

No problem, join the club. I've already got old.

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#51
In reply to #43

Re: Impacts of Rotation of Moon

08/23/2017 9:36 AM

Remember that matter/energy is neither created nor destroyed, but only changes form? There are many forms of energy. And just because one form is not a vector, doesn't mean that ALL forms are not vectors. When you say, "...it doesn't follow that energy is one.", you fail to accommodate the different forms of energy. And vice-versa. Just because one form of energy is a vector, doesn't mean that all forms of energy are vectors; That would would be equally wrong.

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#56
In reply to #51

Re: Impacts of Rotation of Moon

08/23/2017 10:13 AM

hush...go read classical mechanics and get back with us.

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#102
In reply to #51

Re: Impacts of Rotation of Moon

08/27/2017 1:18 AM

Energy is NEVER a vector! That is true for whatever form of energy you wish to discuss.

In what direction does a kWh of electric energy point? In what direction does a calorie of heat point?

At any given instant, an object in circular orbit is moving in a particular direction. At any later time (up to a full orbit later) it is moving in a different direction, but since its orbit is circular, its kinetic energy is constant; no direction involved. Ditto for its potential energy.

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#103
In reply to #102

Re: Impacts of Rotation of Moon

08/27/2017 9:22 AM

Whatever. I said my piece. And, your argument is not convincing to me. I'll just leave it at that.

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#112
In reply to #103

Re: Impacts of Rotation of Moon

08/28/2017 9:25 AM

There is no book like an open book, no mind like a closed mind.

Open up your heart, and allow the sunshine to come forth, and bring peace and light to your heart once more.

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#114
In reply to #112

Re: Impacts of Rotation of Moon

08/28/2017 9:50 AM

I totally agree. Did you notice how dkwarner put "never" in bold capitols? That's a closed mind if I ever saw one. Did you notice how I'm still willing to hear a convincing argument? I'm just not willing to talk to brick wall. I'd rather talk to someone who has brains between their ears instead of concrete.

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#116
In reply to #114

Re: Impacts of Rotation of Moon

08/28/2017 10:50 AM

Dennis, you just don't get it, do you?

Energy is like a lump of coal you hold in your hand. It has a property called mass, so we can size it up as weight, or by measuring its period if we hang it from a string and make a pendulum from it (still measuring the effect of gravity on it). Mass is not a vector, although weight might be considered a sort of vector, since gravity has a directionality to it. We could measure the coal by its volume, by whatever volumetric method you can imagine.

Coal has (depending on its grade) a certain quantity of energy per mass unit (or alternatively per volume unit, but that way is never used that I am aware of).

The coal represents energy, just a volume of natural gas does, and the energy is stored waiting for us to burn it and release the energy in the form of heat. The rate of burning is power (thermal), and the conversion of that heat to mechanical, and then to electrical energy is still just energy (not a vector, but a scalar, just like a meter stick is a scalar representation of distance). A meter stick does not care one iota which direction it is pointed in, although one could attribute that length in a specific direction, and then it represents a vector (scalar , orientation) = vector (in polar coordinates, where the length of the vector is the scalar distance, and the angle with reference to zero (x axis) is the orientation).

Power is not a vector, since when we are discussing power, we typically are not specifically requiring an orientation. However, power can be applied in a direction, then it is a vector (power, orientation) in polar coordinates (or even in spherical coordinates).

Energy cannot be attributed as a directional entity, however momentum can.

Kinetic energy = 1/2 x m x v2 any linear algebraic dot or cross product of a vector with itself is zero, every time the calculation is done. It is not some strange fault of the math. It simply means that (1) the object has energy, since we can calculate that, but it does not imply that energy only exists with an orientation.

Momentum is not the same: Momentum p=mv, where we have the produce of a scalar with a vector, result being a new vector, thus momentum has orientation.

Now does it make better sense?

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#125
In reply to #116

Re: Impacts of Rotation of Moon

08/28/2017 1:49 PM

"Energy is like a lump of coal you hold in your hand. It has a property called mass"? Light has no mass. Does that mean it has no energy? No wonder you can't hold it in your hand or make a pendulum out of it. I know mass is not a vector, but kinetic energy cannot be kinetic if it's not moving (from point A towards point B).

"Coal has (depending on its grade) a certain quantity of energy per mass unit". However, to extract that energy, it has to be released thru a chemical reaction. It's the changes in chemical bonds that release the energy, not the mass itself. We don't have the technology to convert its mass to energy. Oh, wait... If energy has a property called mass, then mass cannot be converted to energy or it will destroy itself. Maybe that's what anti-matter is about. If energy has mass, then how can you separate momentum from KE? Where Momentum goes, so goes KE. Who's side are you on?

"A meter stick does not care one iota which direction it is pointed in, although one could attribute that length in a specific direction". I know that, However, the one using the meter stick should care. Point it in the wrong direction and you'll be using negative numbers when you want positive. Hear about the carpenter who complained, "I've cut this this board 3 times now, and it's still too short!!!"?

If power was not a vector, then we wouldn't need a power factor to distinguish between reactive power and real power for electrical circuits.

"....but it does not imply that energy only exists with an orientation." I never said ALL energy is a vector. I only said KINETIC energy is a vector. Just because one form of energy is a vector, doesn't mean that ALL forms of energy are vectors; That would would be equally wrong. If kinetic energy had no direction, then how could it be moving? In order to move, it has to leave it's present position. If it didn't have a measurable direction AWAY from it's present position, then it couldn't move. And if it's not moving, then how can it be kinetic (momentum or not)? (Light has no momentum [Momentum is not the same: Momentum p=mv. When mass=0, there's no momentum], but it has direction and energy. Try pointing the solar panel away or parallel from/to the light source and see what you get.). Math/numbers may not lie, but mathematicians do make math errors.

I am still not convinced that I'm wrong.

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#126
In reply to #125

Re: Impacts of Rotation of Moon

08/28/2017 5:56 PM

I'll rephrase my earlier statement.

If an object is in as perfectly circular orbit as possible (eg. any geosynchronous satellite), it is remaining at a constant radius from the center of mass of the attracting body (eg. Earth). There is only one radius and only one speed/velocity at which a satellite can be geosynchronous to Earth. At that radius the potential energy is constant. At that speed the kinetic energy is constant; at any point in the entire orbit, it has the same kinetic energy as it does at any other point.

The momentum of the satellite, on the other hand, is constantly changing. The pull of gravity redirects the path of the satellite from a straight line (that it would follow if gravity were not there) into the curve that we call a circle.

Momentum is a vector; any form of energy, including kinetic energy, is a scalar.

You do introduce an interesting point regarding power factor. We do indeed use trigonometry to calculate power factor, but a power factor is neither a vector nor a scalar; it is a pure number, the ratio of two scalars. If you think power is a vector, then you should be able to specify the direction in which it points, but there is no such direction. Does the power of a motor change if you point the motor in a different direction? Of course not!

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#127
In reply to #126

Re: Impacts of Rotation of Moon

08/28/2017 8:44 PM

I think the confusion lies between the abstract concept of energy/power and a specific application/use of energy/power. In the abstract, energy/power can have infinite possible directions. But specific uses require specific forcexdistance. That specific forcexdistance can be changed/altered by gears, pulleys, transmissions, and even gravity. If the distance changes direction, then the work also changes direction.

If a boat is traveling East to West, but the wind is blowing it North to South, then the boat has a East-to-West kinetic energy component AND a North to South component. Combined, it looks like a single value for KE. But remove the wind, and you lose that component of KE. The momentum changes because you lost the energy, not that the energy changes because you lost the momentum. Getting to orbit, the vertical component of KE gets converted to potential energy and both KE and momentum lowers to zero for the vertical component (not the perpendicular component). To get into orbit, you need both vertical and perpendicular components of KE. Once you're there, you can remove the vertical component and stay in equilibrium.

As far as the power of a motor goes, the motor itself has a constant power output relative to direction. However, that power has to be converted into a usable form or it would be senseless to run it. And that new usable form could have vectoral components to it.

How is this wrong?

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#128
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Re: Impacts of Rotation of Moon

08/29/2017 1:05 AM

Please study the concepts of dot and cross products.

The (dot) product of Force (a vector) and distance (a vector) is work, or energy, a scalar.

Work can't change direction, because it has none!

The (cross) product of Force (a vector) and distance (a vector) is torque, a vector pointing perpendicular to both the force and the distance.

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#131
In reply to #128

Re: Impacts of Rotation of Moon

08/29/2017 9:54 AM

Are you 100% sure about that last statement? I see the torque being perpendicular with the distance, yet coaxial with the applied force. Did I also have a brain malfunction here?

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#132
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Re: Impacts of Rotation of Moon

08/29/2017 10:09 AM

As dk stated, it's a cross product, therefore perpendicular to both the force and distance vectors. See e.g. the animation on Wikipedia.

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#133
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Re: Impacts of Rotation of Moon

08/29/2017 10:53 AM

That's correct, torque is a vector pointing along the axis of rotation. If it were parallel to the force or distance vector, or something in between, impossible to come up with a unique direction. Similar for angular momentum.

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#135
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Re: Impacts of Rotation of Moon

08/29/2017 12:00 PM

I am not sure what you boys are smoking, if you are/were. I have never felt that torque manifests itself co-linear with a shaft being turned by it. Angular momentum, yes, I get that. Having mental picture issues coming up with a sensible picture of this in my little old mind.

If what you are saying were true, an unrestricted shaft (able to slide in its bearings) would take off in the z direction upon being accelerated from a stop? I want to call B.S. on that, but apparently, I am just wrong.

So then, mutually perpendicular it must be, no wonder I failed quantum physics. DOH! not! I just lose track of my dimensions.

I definitely get the angular momentum thing. I still cannot produce a mental picture of torque that makes sense to me. Looks like it is trying shove something somewhere, I always thought torque was co-linear with tangential force.

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#136
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Re: Impacts of Rotation of Moon

08/29/2017 12:24 PM

Don't you remember the Right-Hand-Rule? If the fingers point in the direction of the force, and the hand bones point in the direction of the Lever arm, then the thumb points in the direction of the torque.

A torque pointing along a shaft does NOT exert a force in that direction. It is only a convention/definition.

Don't forget that torque is always produced by a force couple (two equal, parallel, non-colinear, forces pointing in opposite directions. In many cases, the second of those two forces is exerted by the bearings on the shaft.

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#138
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Re: Impacts of Rotation of Moon

08/29/2017 12:47 PM

OK, I get that there is a force cancellation once steady-state rotation is reached, otherwise, she just keeps turning faster, and faster.

Seems like I need more than a refresher course. Maybe a refresher brain.

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#140
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Re: Impacts of Rotation of Moon

08/29/2017 1:01 PM

Even during (rotary) acceleration there must be force cancellation if the shaft/axis is to remain in the same location.

of course we only use one of the two forces, and the separation between them, to calculate the torque.

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#141
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Re: Impacts of Rotation of Moon

08/29/2017 1:45 PM

<facepalms>

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#137
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Re: Impacts of Rotation of Moon

08/29/2017 12:29 PM

I think torque being represented by a vector in the direction of the axis is a convention and convenience rather than something that models well what is actually occurring in reality. In which axial direction the troque is represented is fully arbitrary/decided by convention and not anything fundamental, AFAIK.

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#139
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Re: Impacts of Rotation of Moon

08/29/2017 12:49 PM

To me: same thing to myself what I said to someone else a while ago...

insert brain in toilet, pull lever, circle the drain. ( I am a floater)

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#142
In reply to #135

Re: Impacts of Rotation of Moon

08/29/2017 5:52 PM

I may've had a puff or two when I first learnt it (physics degree 45 years ago), but the smoke has cleared and the illusion is still there. It gets complicated, but IIRC it's very useful for explaining gyroscopic action.

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#143
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Re: Impacts of Rotation of Moon

08/30/2017 9:09 AM

Thanks to both of you, for patiently showing me the error of my way.

I certainly do get angular momentum connection to gyroscopes, and if I really had thought about the maths involved, I would have understood better about force input to a gyroscopic system, and how it reacts, etc.

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#144
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Re: Impacts of Rotation of Moon

08/30/2017 10:53 AM

You're welcome! It's been over 22 years since I quit teaching physics, so this was a good refresher for me as well! Now if we could somehow get Dennis to join the group...

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#145
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Re: Impacts of Rotation of Moon

08/30/2017 11:42 AM

see #130. Maybe he is washing his fur.

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#146
In reply to #144

Re: Impacts of Rotation of Moon

08/30/2017 12:54 PM

Sadly think it'll be a long time before that happens.

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#147
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Re: Impacts of Rotation of Moon

08/30/2017 5:18 PM

Say John. What is the name used in the UK for the cooking utensil I know as a "Pressure Cooker"?

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#151
In reply to #147

Re: Impacts of Rotation of Moon

08/31/2017 7:05 AM

We call them "Pressure Cookers"!

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#153
In reply to #151

Re: Impacts of Rotation of Moon

08/31/2017 11:05 AM

Thanks! When I mentioned them early in this discussion, it occurred to me that they might have a totally different name over there, similar to torch vs. flashlight...

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#148
In reply to #144

Re: Impacts of Rotation of Moon

08/30/2017 9:16 PM

I dunno. Maybe if you included a link for me to study what you were referring to, I could give it some attention. No promises tho.

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#149
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Re: Impacts of Rotation of Moon

08/30/2017 10:16 PM

You can search for lots of help on that.

Here is one possible starting point. I only viewed the first few minutes, so I don't know how useful you may consider this particular one. He starts out hinting that it is obvious that the result of a dot product is always a scalar and that of a cross product is always a vector. The statement is true, except to me it is NOT obvious. It is simply a fact that must be learned...

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#152
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Re: Impacts of Rotation of Moon

08/31/2017 10:49 AM

Okay, I checked it out, along with some other explanations. The thing that stands to me is exactly what you said, "The statement is true, except to me it is NOT obvious. It is simply a fact that must be learned...". And that's the whole problem. When you start out by saying ,"Let's define...", then it becomes a law and not an explanation. What I'm trying to do is explain "what is", instead of defend a law. When you end up defending a law, no explanation is produced. The statement ,"because that's the law,", does not explain "what is". Then, you wind up trying to mold reality into the law, instead of understanding reality as it is.

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