The Simple Pendulum

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The Simple Pendulum
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Energy Considerations
The Pendulum Pennant
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A falling pendulum
Assuming that no external work is done on the
pendulum bob
Max velocity (at bottom)
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A pendulum being raised up
External work must be done to raise the bob.
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Tension in the String
To analyze the pendulum bobs motion, break the
gravitational force into its centripetal (inward
pointing) and tangential (perpendicular to the
string) components.
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The force due to gravity on the pendulum bob is
always the same. However, as the bob swings
downward, the centripetal force (pointing inward)
increases while the tangential force (pointing
perpendicular to the string) decreases.
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Using a little right triangle trigonometry
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(No Transcript)
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l
T
Fcentripetal
q
Fg
Ftangential
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0o 90o
180o
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Tension
0o 90o 180o
270o 360o (0o)