Opposite Directions

It sounds like the 'launcher' is already moving, then?

If that's what you're saying and the launcher is moving +X m/s with respect to the ground and the launcher fires a projectile -X m/s with respect to the launcher, then yes, with respect to the ground, the projectile will appear to not move at all.

The velocity of the projectile with respect to ground is equal to the velocity of the projectile with respect to the launcher plus the velocity of the launcher with respect to ground. +X + -X = 0.

Is that what you're talking about?

Thank you,herzoa. Mostly I was trying to provoke more stories from folks who actually tried this. My comment about the bowling ball and semi truck is true. The ball came out the back of the trailer and simply fell to the ground.(much to the consternation of the ball and my friend's big toe)

Qman,

You and your mates have already completed empirical testing that can not be challenged so your answer is "YES". I look forward to your next brain teaser.

I with you Mike.

Who can argue with empirical testing, especially if he has a spare bowling ball up his sleave.

Mike,

Do you have anything to do with a company that starts with the letter "T"? If so, you and I have a close relationship ( metal-wise).

Yes

(excluding anything less massive than, say a B-B)

Why would that make a difference?

If you're assuming no gravity and no atmosphere, why limit it to things larger than a BB? It will work for anything with non-zero mass, provided the speeds involved are sufficiently smaller than light-speed so that relativistic effects can be ignored. To account for relativistic effects, you have to apply the Lorentz transformations, which I'm too lazy to look up.

Of course, all of the above depends on your definition of "standing still," which you already know, or you wouldn't have put it in quotes.

(Hey, WAIT a minute! You're not even asking a question! This was just a trick to tell everybody about the time you got drunk and ruined a bowling ball. Wish I coulda seen that.)

You got me!

If I understand this correctly, I can stand in the back of a fast moving truck with the rear door open. I can then fire my rifle at the pursuing police car, and the bullets will just fall to the ground and not hit the police car?

Well if the police car is pursuing... then the car will run into the bullets! Talk about a unique defense case!

NO NO !...

The bullets will be stationary, but the police car will drive into them before they hit the ground!!!

Del

Wow, bob c. Does your truck go that fast?

No not really, It's only half fast. You asked for that. Sorry.

The heck with the bullet. Roll the bowling ball!

This is true because the projectile in the launcher is already traveling at that speed forward, so when fired backwards, the projectile is actually slowed to a stop (with every thing perfect) - The Energy of the Projectile moving forward is transfered to the launcher and thus to the platform. The Projectile will then stop and the launcher would increase in speed based on the mass ratios.

What about the dynamics of a real projectile fired from a a barrel of a firearm?

Even if the displacement is effectively nil from the respective axis, would there not be some rotation on a projectile most times?

So rather than standing still, would it not spin around like a planet does?

Just some thoughts to go with my tea this morning!

=)

I guess that would depend on the Launcher - if it was a rifled barrel there would be spin and would be at the same rate. With no Gravity and in a Vacuum, effectively leaving the projectile spinning like a top or gyro but stationary.

We could spin the launcher in the oposit direction and speed, but that sounds like a lot of effort to have a net result of a stationary object floating in space.