Chapter P.2, Problem 5P

The following passages and associated questions are based on the material of Part II.

Big Air

A new generation of pogo sticks lets a rider bounce more than 2 meters off the ground by using elastic bands to store energy. When the pogo’s plunger hits the ground, the elastic bands stretch as the pogo and rider come to rest. At the low point of the bounce, the stretched bands start to contract, pushing out the plunger and launching the rider into the air. For a total mass of 80 kg (rider plus pogo), a stretch of 0.40 m launches a rider 2.0 m above the starting point.

If you were to jump to the ground from a height of 2 meters, you’d likely injure yourself. But a pogo rider can do this repeatedly, bounce alter bounce. How does the pogo stick make this possible?

A. The elastic bands absorb the energy of the bounce, keeping it from hurting the rider.

B. The elastic bands warm up as the rider bounces, absorbing dangerous thermal energy.

C. The elastic bands simply convert the rider's kinetic energy to potential energy.

D. The elastic bands let the rider come to rest over a longer time, meaning less force.