Question

After attending Physics 10's lecture, Max decided to test Newton's 2nd law. He jumps from elevator position.
a. On Max'x first jump he bends his knees when he hits the ground. Explain why Max was able to make this jump safely.
b. He then lands straight legged, he is rushed to the hospital. Why did he get hurt?

Answer 1

Impulse. Impulse is equal to force*time. It is also equal to the change in momentum due to that force applied over time. In each case, Max's change in momentum is the same, but when he bends his knees, the time it takes to change his momentum is much bigger, therefore the maximum force is smaller. When he lands straight legged, the time is very small, so the force is large. The damage to Max's legs came from the high force.