Question

In: Physics

An early method of measuring the speed of light makes use of a rotating slotted wheel....

An early method of measuring the speed of light makes use of a rotating slotted wheel. A beam of light passes through a slot at the outside edge of the wheel, as in the figure, travels to a distant mirror, and returns to the wheel just in time to pass through the next slot in the wheel. One such slotted wheel has a radius of 8.8 cm and 100 slots at its edge. Measurements taken when the mirror is L = 1100 m from the wheel indicate a speed of light of 3.0 x 105 km/s. (a) What is the (constant) angular speed of the wheel? (b) What is the linear speed of a point on the edge of the wheel?

Solutions

Expert Solution

a)   Here, t = 2L/c

                    = 2 * 1100/(3 * 108)

                    = 7.33 * 10-6 s

   theta = (2pi)/100

              = 0.0628 rad

Thus,   the (constant) angular speed of the wheel = theta/t

                                                                               =   0.0628/(7.33 * 10-6)

                                                                             = 8567.53 rad/s

b)   the linear speed of a point   = r * w

                                                  = 0.088 * 8567.53

                                                   = 753.94 m/s


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