Table of Waves & Sound Demonstration

List of Mechanics Equipment & Supplies

Lecture Demonstrations

Simple Pendulum, 3A10.10

Topic and Concept:

pira200 Listed

Location:

Abstract:

Suspend a simple pendulum from a ringstand or hold by hand, and provide some energy allowing it to oscillate.

Equipment

Location

ID Number

Ball on a String

ME, Bay A2, Shelf #1 or hanging in tack cabinet near main lecture halls

Important Setup Notes:

Setup and Procedure:

  1. If using the rod & clamp to suspend the pendulum (the preferred method), attach the support rod to the bench with the clamp.

  2. Attach a cross-bar on the top using a right-angle bracket, and slip the loop end of the string over the rod.
  3. If desired, use a binder clip to keep the string in place.
  4. Pull the ball back from equilibrium to some arbitrary height while keeping the string taught and release.
  5. If using your hand, suspend the pendulum from one hand.
  6. Using the other free hand, pull the ball back from equilibrium to some arbitrary height while keeping the string taught and release.

Cautions, Warnings, or Safety Concerns:

Discussion:

When the ball is pulled back from equilibrium, at the point of lowest potential, it is given potential energy. Once released, there is a net force on the ball due to gravity so the ball falls. The potential energy changes to kinetic energy as the ball falls. Thus the speed of the ball increases reaching a maximum at the point of lowest potential. The amount of kinetic energy the ball has is dependent on it's height at a given time being constrained by the conservation of energy: Etotal = U + T where U is potential energy and T is kinetic energy. The ball has momentum while it is moving, but this is constantly changing as the direction of the tension force is constantly changing with displacement angle. If the system were perfectly conservative (i.e. there was not any air resistance or friction), the ball would oscillate indefinitely swinging in a plane reaching a maximum height (the height up to which the ball was originally pulled) and stopping then reversing direction. In practice, however, there is always energy loss in such systems, and the pendulum will eventually come to a halt and assume its original equilibrium position at the point of lowest potential.

pendulumAnimation.gif

Ball01-250.jpg

Ball02-250.jpg

Ball03-250.jpg

BrassBall02-250.jpg

TennisBall03-250.jpg

Videos:

References:

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fw: Simple_Pendulum (last edited 2018-07-18 18:29:14 by srnarf)