The motors that drive airplane propellers are, in some cases, tuned by using bea

Question

The motors that drive airplane propellers are, in some cases, tuned by using beats. The whirring motor produces a sound wave having the same frequency as the propeller.

Part A

If one single-bladed propeller is turning at 574 rpm and you hear a 2.00 Hz beat when you run the second propeller, what are the two possible frequencies (in rpm) of the second propeller?

Part B

Suppose you increase the speed of the second propeller slightly and find that the beat frequency changes to 2.10 Hz . In part (A), which of the two answers was the correct one for the frequency of the second single-bladed propeller ?

Part C

How do you know the answer in part (B) to be correct? Explain.

Explanation / Answer

A) 574 +/- 2*60 = 574 +/- 120

so 454 or 694 Hz

B and C) so if increasing rate increases the bat it had to be faster than first

so 694 Hz

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