The Power of the Pendulum

Pendular motion A pendulum is simply a mass on a rod, rope, string, etc, that is allowed to swing freely from a pivot.

A pendulum is an energy converter The bob is raised, adding potential energy, and when it is released… The potential energy is converted to kinetic energy and back to potential energy repeatedly. In the real world, a pendulum does not continue swinging indefinitely because it is losing energy due to the interaction with air molecules.

A Pendulum obeys a formula T2 = 4π2l/g Where T = period or time for one complete oscillation and g = gravity and L = length of the pendulum measured from the pivot to the center of the bob’s mass. The period for a pendulum depends on only two things: 1) length 2) gravity However, this formula only applies if the release angle is less than 15 degrees.

Video clip #1: Allen’s Pendulum stand This video clip focuses on a group of pendluae mounted in a stand. The bobs are golf balls. The length determines the period of each pendulum.

Video clip #1: Allen’s Pendulum stand Allen’s Pendulae Please answer questions 1 - 2.

Video clip #2: Trust exercises in physics Dr. Lewis and the deadly bowling ball Let’s measure the period of the ball, then calculate the expected length. Now, estimate the length of the rope. Answer questions 3 - 6.

Video clip #3: completing a 360 Don’t try this at home… Measure the period in the first 6 s of video, then calculate the expected length. Remember to measure the length of the pendulum to the center of the mass. Now estimate the length. Answer questions 7 – 9.

Video clip #4: Bone cages – Pirates of the Caribbean The natives built the cages after the arrival of the pirates… Measure the period of the swing – you’ll only get ½ of the period in the clip. The best location is 55 – 64 s. Calculate the expected length of the rope at time = 57 s. Estimate the length of the rope. Answer questions 10 – 12.

Video clip #5: The making of the Bone cages – Pirates of the Caribbean This is how they did it… Measure the period of the pendulum, then calculate the length. Answer 13 – 14.

Just for Fun, Resonance and Rotating the Black PearL They’ve got to flip the ship What does the crew have to do to flip the ship?