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Do your own work on this assignment.

1.      Clocks with rotating hands measure time in terms of the angle, A, swept out by the hand during the time interval, t.  Write an equation for t in terms of  A and the period T of the clock.

 2.      In calculations, it’s more common to use the frequency of the clock rather than its period.  Frequency is what a stroboscope measures directly.  Rewrite your equation from problem 1 in terms of frequency, f, instead of period.

 3.      The photograph on this page shows two rotating discs, A and B. Although each disc has a single hand, two images of the hand are seen because the discs were lit by sequential bursts of light from two flash units. The frequency of disc B was measured with a stroboscope and found to be 50.5 Hz.  Print the photo. Using a ruler or straightedge, extend the 2 lines on each disc far enough that you can use a protractor to measure the angles subtended by the lines. Then measure the angles to the nearest half degree. Write the measured angles below.

Angle for disc A to the nearest half degree =

Angle for disc B to the nearest half degree =

4.  Using your equation from step 2, calculate the time interval between the bursts of light. Express your result in seconds to three significant figures.

5.  Using the time interval calculated in step 4, calculate the frequency of disc A. Express your result in Hz to 3 significant figures.