1 The Swinging Pendulum 8 th Grade Science Butler Middle School Lowell, MA Bob, Paul & Ms Adams April 4, 2012

2 Must See TV Tonight Ch 2, WGBH, 9pm This may help you with MCAS

3

4

Having Fun with a Pendulum

All PE Top Speed KE All PE Swinging Pendulum Assume: Negligible Friction and Air Resistance Also assume string has negligible mass bob Unbalanced Force! Pivot Point No Unbalanced Forces Top Speed KE No Unbalanced Forces

The bob’s Energy All Potential at the high points. All Kinetic at the low point. Is the kinetic energy equal, bigger, or smaller than potential energy at the high point? In between the ‘bob’ has both potential & kinetic and they are continuously transforming into each other.

The bob’s Motion Between the high points and the low point: The bob is either speeding up or slowing down. This requires an unbalanced force. The change in speed is called: __________ At the high points the bob’s speed is zero and a change of direction occurs. At the low point the bob’s speed is maximum and there is no unbalanced force. What does Newton’s 1st Law say about this?

Vocabulary One Swing of the bob is also called: One Round Trip One Back and Forth One Cycle One Vibration Period: Time for One Swing of the bob Frequency: Number of Swings per Second

Measure Period by timing 10 swings, then divide by 10 Period = Total Time / 10

Your Experiment Determine how length of string and mass of the bob affects period. Can you create a pendulum with a period of 1 second?