If you wear kneepads when skating, after a fall to your knees it will take 3 times as long for them to come to a rest. How does this affect the change in momentum of your knees during the fall?
A. The change in momentum is the same with or without the kneepads
B. The change in momentum decreases by a factor of 9
C. The change in momentum decreases by a factor of 3
D. The change in momentum increases by a factor of 3

Question

If you wear kneepads when skating, after a fall to your knees it will take 3 times as long for them to come to a rest. How does this affect the change in momentum of your knees during the fall?
A. The change in momentum is the same with or without the kneepads
B. The change in momentum decreases by a factor of 9
C. The change in momentum decreases by a factor of 3
D. The change in momentum increases by a factor of 3

chillout · Answer

Correct answer is A.
The pads will only change the coefficient of friction between your knees and the floor.

Remember that momentum is defined as $p=mv$ and  the change in momentum will be the same since you have the same initial and ending velocities!