Answer:
40. 383 Hz, 0.9 m
6. 20.78 m/s
Explanation:
40. You know the pitch will be increased when the train is moving toward you. The only answer choice that is greater than 350 Hz is the one shown above.
Using the formula shown in the attachment, we compute the observed frequency to be ...
... f' = (343 m/s)/(343 m/s -32 m/s)×(350 Hz) ≈ 1.102893×350 Hz ≈ 386 Hz
The wavelength is given by ...
... λ = v/f = (343 m/s)/(386 Hz) ≈ 0.8886 m ≈ 0.9 m
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Comment on the answer choice
If you erroneously use the frequency modification formula f'=(v+vo)/v·f, then you get 382.7 Hz ≈ 383 Hz. We suspect an error in the answer key. Have your teacher show you how to work this problem.
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6. The velocity can be computed from the acceleration and distance covered by ...
... v = √(2ad)
... v = √(2·9.8 m/s²·22 m) = (√431.2) m/s ≈ 20.77 m/s
The closest answer among those offered is 20.78 m/s. Again, you should have your teacher show you how to work this problem to arrive at the offered answer.
