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TheSwinging Pendulum

8th Grade ScienceButler Middle School

Lowell, MA

Bob, Paul & Ms AdamsApril 4, 2012

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Must See TV TonightCh 2, WGBH, 9pm

This may help you with MCAS

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Having Fun with a Pendulum

AllPE

TopSpeed

KE

AllPE

Swinging Pendulum Assume: Negligible Friction and Air Resistance

Also assume string has negligible mass

bob

Unbalanced Force!Pivot Point

No UnbalancedForces

TopSpeed

KE

No UnbalancedForces

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?

VocabularyOne 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?