Question

MEDAL GIVEN TO CORRECT ANSWER.
Two football players collide on the field. Before the collision, their total momentum was 450 kgm/s to the north. What is their total momentum after the collision?

A. More than 450 kgm/s north
B. 450 kgm/s north
C. Less than 450 kgm/s north
D. 450 kgm/s south

Answer 1

I believe it would be C since potential and kinetic energy was lost during the impact. c:

Answer 2

Momentum is conserved as long as there are no EXTERNAL forces acting on the system. The question does not say that there are external forces on the system, so momentum should remain the same.

To me, the best answer is B. 450 kgm/s to the north.

Answer 3

@HomeschoolGrad is right

Answer 4

HomeschoolGrad: but the problem does say "football players" and "collide on the field." The answer is C.

Answer 5

Hello @Walidhubbi, :)

Well, the problem could also have said "cars", "trucks", or any other kind of object, and it still would not change the nature of the question.

Also, while it is true that the two players collide on a field, the problem fails to inform us whether there are any EXTERNAL forces involved. Sure there is no doubt there must be many INTERNAL forces acting on both players when they collide, but as long as there are no external forces, momentum MUST be conserved.

Does the question seem ambiguous? A little--it would have been better if it had explicitly said "assume there are no external forces on the players."

There is always the chance that this is a "trick" question, but I don't think so.

To me the best answer is still B.

Answer 6

i do believe that the answer is 450kgm/s north according to law of conservation of momentum. It must be 450 as there are no external forces on it and it should be due north as if it is in south there would be sign change.

Answer 7

B must be the answer. momentum must be conserved during collision