Does Equal Force Result in Equal Momentum for Different Masses?

  • Thread starter Thread starter blackout85
  • Start date Start date
  • Tags Tags
    Momentum
Join the discussion
Registration is free. Ask a follow-up in this thread, or start your own.
1 reply · 9K views
blackout85
Messages
27
Reaction score
1
Please check over my work

Two bodies of unequal mass, placed at rest on a frictionless surface, are acted on by an equal horizontal forces for equal times. Just after the forces are removed, the body of greater mass will have:
The body of greater mass will have the the greater speed, the greater acceleration, the smaller momentum, the greater momentum, or the same amount as the other body.

Would the answer be the larger body would have the same amount amount of momentum as the other body because P(before)=P(after). The momentum would have to come out the same in order for that to be right.

second question:

A 0.2kg rubber ball is dropped from the window of a building. It strikes the sidewalk below at 30m/s and rebounds up at 20m/s. The impulse during the collision would be:

my work:
0.2 (-30m/s) - 0.2 (20m/s) = 10 upward

Please let me know if I am on the right track and let me know where I might have gone wrong:redface:
 
Physics news on Phys.org
blackout85 said:
Would the answer be the larger body would have the same amount amount of momentum as the other body because P(before)=P(after). The momentum would have to come out the same in order for that to be right.

Yes, but you should use the fact that the impulse of the force equals the change of momentum, and since the impulse is equal for both bodies, you have F*t = m1v1 = m2v2.

blackout85 said:
A 0.2kg rubber ball is dropped from the window of a building. It strikes the sidewalk below at 30m/s and rebounds up at 20m/s. The impulse during the collision would be:

my work:
0.2 (-30m/s) - 0.2 (20m/s) = 10 upward

Please let me know if I am on the right track and let me know where I might have gone wrong:redface:

Looks good.

Edit: the change in momentum (i.e. the impulse) should actually be: [tex]0.2\cdot 20\vec{j}-0.2\cdot(-30)\vec{j}=10\vec{j}[/tex], which means 10 upwards.
 
Last edited: