1M40.10 Suicide Pendulum

Concepts

Conservation of energy, demonstrated in a very dramatic manner

Overview

The bowling ball pendulum is held up to the demonstrator's face and is released. Because of conservation of energy, the ball will not swing higher than the height at which it was released (in fact, because energy is lost during the swing, the ball falls slightly short of the demonstrator's face when it completes one full period). To paraphrase Leigh, physicists believe in conservation of energy and therefore have complete confidence that if they release the ball right next to their head that the ball will swing back and stop, not continue on and smash their head. The apparent danger of having one's head smashed gives the demonstration great crowd appeal. The demonstration usually draws an audible response from the audience. Note: setup time during the lecture is short, but setup time before the lecture is long (this setup is usually done by a technician).

Details

Equipment

  • [1] Bowling ball suspended from the ceiling on a cable

Important Notes

  • The bowling ball is heavy and can cause serious bodily harm. Release, DO NOT PUSH, the bowling ball away from your face. Note that it is difficult not to flinch when the ball swings towards your face. Practice this demo in advance and perform with extreme caution!
  • Care must be taken not to hit benches and other objects with the pendulum

Script

  1. Keeping the cable taught, pull the pendulum (bowling ball) to one side until it touches your nose. Be sure to stand straight and still.
  2. Release the pendulum, taking care not to move your face.
  3. Remain very still while the pendulum swings through one full period.

 

Additional Resources

References

  • PIRA 1M40.10

Disclaimer

  • Don't attempt this at home!

Last revised

  • 2018

Technicals

  • An eye hook was screwed into a bowling ball.
  • The bowling ball was suspended from the ceiling by a steel cable.

Related AV

Related demos

 

If you have any questions about the demos or notes you would like to add to this page, contact Ricky Chu at ricky_chu AT sfu DOT ca.