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, 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 11.0 cm and 800 slots at its edge. Measurements taken when the mirror was L = 500 m from the wheel indicated a speed of light of 3.0 x10^5 km/s.(adsbygoogle = window.adsbygoogle || []).push({});

My work:

Conversions:

.11m

3.0x10^8m/s

L = 500m

Arclength = 2pi*.11m

Rotational speed = (2pi*.11m)/800

Rotational speed = ((2pi*.11m)/800) * Speed of Light

Rotational speed = 259181.39 rads/s <- This is wrong

I did (Arclength/Slots) * Speed of Light to calculate 1 slot's worth.

What was the (constant) rotational speed of the wheel? (rad/s)

What was the translational speed of a point on the edge of the wheel? (m/s)

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# Homework Help: Rotational Speed with the Speed of Light

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