A-LevelPhysicsWaves9702/12 · May/June 2017 · Q241 Mark

A bicycle gear wheel is a disc with 50 'teeth' equally spaced around its edge, as shown. The gear wheel is rotated 10 times each second. A springy strip of metal is vibrated by the rotating 'teeth'. The metal strip produces a sound of frequency that is equal to the frequency of vibration of the strip. [Figure shows a gear wheel with 50 teeth, rotating. A springy strip of metal is held by a fixed clamp and touches the teeth of the gear wheel.] The speed of sound in air is 330 ms⁻¹. What is the wavelength of the emitted sound?

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A0.66 m

B1.5 m

C6.6 m

D500 m

✓ Correct answer

A: 0.66 m

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