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A boy standing idle sounds a whistle to his friend at a distance of 1200 m moving away from him in a speeding car at 108 kmph. Find the duration (seconds) after which his friend is going to hear him. (Speedof sound = 330m/sec).
A3.6
B4
C40
DNone of these
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The logic behind this question is to get that extra distance which the car will cover while the sound approaches him while traveling 1200m.
Time taken by sound to cover 1200m =1200/330= 40/11 sec= 3.63sec (i)
In this time of 40/11sec the car will cover an extra distance of 30m/sec*40/11sec= 109.09m
So extra time taken by sound to cover this distance will be= 109.09/330= 0.33sec (ii)
Adding both the times we get 3.96 approx = 4 sec.
Time taken by sound to cover 1200m =1200/330= 40/11 sec= 3.63sec (i)
In this time of 40/11sec the car will cover an extra distance of 30m/sec*40/11sec= 109.09m
So extra time taken by sound to cover this distance will be= 109.09/330= 0.33sec (ii)
Adding both the times we get 3.96 approx = 4 sec.
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