Physics education research, electronic materials, and the musings of Christopher Moore, Ph.D.
Physics education research, electronic materials, and the musings of Christopher Moore, Ph.D.
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George claims that it is possible for a stationary object which is struck by a moving object to have a larger final momentum than the initial momentum of the incoming object, but Lesley maintains that this would violate the law of conservation of momentum. Who is correct? Justify your decision.
I thought that George was right, but only if the struck object has a tiny mass, its momentum will still be conserved, but I thing I am wrong
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Well, to have a large momentum is can either have an extremely large velocity or a very large mass. You could theoretically have a mass the size of a marble moving with a large speed, and a mass the size of a large rock moving at a small speed and both having the same momentum.
So when would it be possible to explain an interaction where the final object is now moving with a larger momentumv - is it possible? Well, its quite simple. Physics states quite clearly that the sum of the momenta before the collision, must equal the sum of the momenta after the collision: there are no reasons to suggest that the final velocity should equal a greater sum than the original momenta:
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Well, I think George is right and this is not violating the law of momentum.And it doesnt depend on masses of the objects. If moving object bounces backwards, the first object (the stationary one previously) MUST have a larger momentum, otherwise the sum of momenta after the collision would be larger then the initial sum which would be a violation of the momentum conservation law.
M2*U2 = M1*V1-M2*V2 // where M2 is the mass of the moving object
M1*V1=M2*U2+M2*V2
therefore M1*V1>M2*U2
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you said '' the first object (the stationary one previously) MUST have a larger momentum, ''
How can a stationary object have a large momentum...???? It cannot have a momentum at all. It'sonly until after a collision, momentum is conserved and transferres that same quantity of force due to their kinetic energy. Nothing should accelerate a final momentum after the collision unless acted upon by some external force. This is what inertia is all about.
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When the object is struck it is not stationary any more! And in case the striking object bounces backwards the first object must have larger momentum than of the striking one before collision in order to conserve the sum of momenta. The sum of momenta is conserved, not a momentum of a separate mass. Whether the second(striking object) moves back after collision? we dont know. To answer this we must know what the masses ratio is, and what is the nature of collision(whether it is an elastic one or not).
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