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Observing the Damping of the Motion
of a Simple Pendulum
| 1.
Preparation: |
a) A
"damped" oscillation is one in which an external force
causes the amplitude to decrease. The damping of the
motion of the pendulum is due to air resistance. Why is it
reasonable to expect that the average magnitude of the force of
air resistance acting on the bob will depend on the amplitude of
the oscillations? |
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b) Read about
the basic properties of exponential graphs. |
| 2. |
Set up
the apparatus as shown below. A 5 g or 10 g mass will be found
suitable for the pendulum bob. Length of pendulum about 40 cm. |
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| 3. |
Start the pendulum
oscillating with an initial amplitude (r0) of about 15cm.
Allow the pendulum to oscillate and estimate the amplitude of the
oscillations after 10, 20, 30 etc oscillations. |
| 4.
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Plot a graph of
amplitude against number of oscillations.
Try to prove that this graph is (approximately) exponential. |
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