He is a physics teacher showing a class that a pendulum never swings back higher than where it started. Hold the ball to your nose, let go and it stops just short of your face. Give it a little shove as you let go, and it doesn’t.
A man lets go of a bowling ball, and a few seconds later he is on his way to hospital. He didn’t drop it on his foot. What happened?
Give me a hintThe hint
The ball is hanging from the ceiling on a rope.
Reveal the answerHide the answer
His pendulum demonstration went wrong
Source: Traditional, from Jed Hartman’s list of situation puzzles