Calculation of mass

Assuming we are talking about mass and not weight, as per conservation law

mass+energy = constant.

A body in motion has a Kinetic energy = ¹/₂ mv²

So total mass+energy = m + ¹/₂ mv²

But V is with respect to what frame of reference ?

With respect to the frame from which it is moving, its mass apparant is same (m) assuming the energy is acquired from external source

ir m-Δ if it is from itself

However if I consider the body itself as its frame of reference, its mass must have increased due to the energy absorbed by it from the external source (first case)

If I throw a baseball at you, it will weigh the same when it leaves my hand as when it hits you in the head. If I throw it harder, it will have more inertia and energy, but will still wiegh the same.. If I throw it hard enough.... okay I won't say it. I will say this.. based on what you have written, this question is too junior to be asked here. this is an engineering forum, not a grade 8 science class.

chris

So I think "Guest" has given you a pretty good answer. Objects have mass, but weight is something else again!

It doesn't help that they spend years in school telling us that an object weighs 5 lbs. or some other number of kilograms in the metric system. Then, one day, they spring the concept of "mass" on us and use metric terms like "Kg" or "gram" to describe it.

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It doesn't help that they spend years in school telling us that an object weighs 5 lbs. or some other number of kilograms in the metric system. Then, one day, they spring the concept of "mass" on us and use metric terms like "Kg" or "gram" to describe it.

[/quote]

Neither does it help that mass can be refferred to as "inertial", "passive gravitational", "active gravitational", and even "relativistic". Wiki defines it as a resistance to acceleration or change in velocity, this or that nasa page defines it as a measurement of the amount of matter or material ...

The weight is the gravitational force due to mass*gravitational acceleration (w=m*g)

If your body moves from the earth surface to the moon the g changes and so the weight. Otherwise, if your body moves on the earth surface you can consider that g is costant.

About the mass. Actualy the mass depend on the velocity of the body as described by the relativity theory of Einstein... but if the body velocity is "small" (less than 50-60% of the light velocity=300000 km/s) you can consider with high precision that the mass is constant.

Smithkumar,

The best responses to your question are 3 & 5. I would IGNOR #2. he has a Mass and Weight problem in his head (Big Headed, Conceited).

Remember Chrisg288 ------People who think they know it all seldom know anything, since they only live in the world they know.

Everybody should remain open to learning something new each and everyday, or it is a waste of a day.

A body in motion can appear to have more or less mass by it's combined modal and rigid body response. As an example, a cantilever beam in a harmonic response (non axial) will only respond with it's Modal Mass Participation. The mass participation will be less than the mass of the beam.

Now, if we take a simple beam traveling at a constant velocity and then excite it's simple beam bending harmonic, we no longer get constant velocity (over time). If one were to caculate the amount of mass participating in the dynamic response of the beam, it would be greater then 100% because we have a rigid body response superimposed onto a harmonic response.

1. The OP asked about weight not mass, and I answered correctly.

2. the question is so vague that it requires many assumptions to be made, and therefore the question is either unanswerable without further input, or it is too junior for this forum.

I apologize for my sarcasm. that was unnecessary.

Well, we've grown to expect that from the Canadians.

I learned from the best! (you)

The saying says that sarcasm is the lowest form of wit.............but it sure can make you laugh!

I'm with you on this one Cris

and...............Here Vermin you leave the Canadians alone They are bonza blokes!!!!

Canadians are lucky to have America so close. It helps keep them in place and holds them down.

Without America they would float away since they are all Air Heads.

don't cha know EH......................

Not sure that i understand it (never heard of this concept)- any links on this subject ?