Using a Stroboscope to Make a Propeller Appear Stationary

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AI Thread Summary
A stroboscope can create the illusion of a stationary propeller by flashing at a specific rate that matches the propeller's rotation. For a three-bladed propeller rotating at 14.4 revolutions per second, the shortest time between flashes required to achieve this effect can be calculated based on the angular displacement of the blades. Each blade covers 120 degrees per rotation, so the light must flash every time the propeller rotates by this angle. The solution involves determining the timing of the flashes in relation to the propeller's speed. Proper calculations will yield the shortest and subsequent flash intervals needed for the desired visual effect.
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Homework Statement



A stroboscope is a light that flashes on and off at a constant rate. It can be used to illuminate a rotating object, and if the flashing rate is adjusted properly, the object can be made to appear stationary.
(a) What is the shortest time between flashes of light that will make a three-bladed propeller appear stationary when it is rotating with an angular speed of 14.4 rev/s?
s

(b) What is the next shortest time?

Homework Equations





The Attempt at a Solution



not sure where to start.
 
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When the propellor rotates by 120 deg, it looks the same. The light should flash again by the time the propellor has done this.
 

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