Gymnasts often practice on foam floors, which increase the collision time when a gymnast falls. What effect does this have on collisions?

Question

The change in momentum needed to stop the gymnast is increased.
The change in momentum needed to stop the gymnast is decreased.
The force exerted by the floor on the gymnast decreases.
The force exerted by the floor on the gymnast increases.

Answer 1

When a gymnast falls on a foam floor, the foam increases the collision time, which allows for a longer duration over which the gymnast's momentum is brought to zero. This extended time reduces the average force exerted during the collision according to the impulse-momentum theorem, which states that impulse (force multiplied by time) is equal to the change in momentum.

Since the momentum needs to be stopped (i.e., brought to zero), increasing the time over which that change occurs results in a smaller average force being exerted.

Therefore, the correct statement is:

The force exerted by the floor on the gymnast decreases.