No. Terrance cannot move the sled. This is because, the force that he produces is 80*3 Newton’s, which is only 240 Newton’s, but since the sled needs a force of 250 Newton’s, he cannot move the sled (even though the difference is only by 10 Newton’s).
Answer: 529.9 Hz
Explanation:
Here we need to use the Doppler equation, so we have:
f' = f*(v + v0)/(v - vs)
Here, f is the frequency = 500Hz
v is the velocity of the wave, = 334m/s
v0 is the velocity of the observer = 20m/s
vs is the velocity of the source = 0m/s
Then we have:
f' = 500Hz*(334m/s + 20m/s)/(334m/s) = 529.9 Hz
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