Easy one :)
Classical Mechanics
Level
2
A man is facing a wall 34 m away from him. He produces sound towards the wall and starts moving in the backward direction, with a speed of 1.7m/s. When will he hear his echo? (Given speed of sound = 340m/s)
Please upvote if you like the problem. :)
None of the above
0.21s
0.203s
0.201s
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1 solution
Time taken by sound to travel till the wall and come back to initial point of man = (2 x 34)/340 = 0.2s ------(1)
In 0.2s, distance travelled by man backward = 0.2 x 1.7 =0.34m
Time taken by sound to travel 0.34m = (0.034/340) = 0.001s --------(2)
Total time = 0.2s + 0.001s =0.201s
Therefore time taken to hear the echo = 0.201s