Question:
A man moves from a place P to another Q with a constant speed of 10 m/sec. and then he returns back to P again with the same constant speed along the same route. Calculate the average speed of man.
Answer:
We know that Speed = Distance / Time; Average speed = Total path length / Total time taken
Let the time taken for the forward journey (PQ) and reverse journey (QP) be t1 and t2 respectively.
Let the distance PQ be S. Hence, PQ = QP = S m
For the forward journey PQ = S/ t1 = 10 m/s which implies t1 = S/10 sec
For the reverse journey QP = S/ t2 = 10 m/s which implies t2 = S/10 sec
Total time taken = t1 + t2 = S/10 + S/10 = 2S/10
Total Distance = S + S = 2S
Average speed = Total path length / Total time taken = 2S / (2S/10) = 10 m/s
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