How far from a cliff should a boy stand in order to hear the echo of his clap 0.9s later? (Speed of sound in air = 330 ms^{-1})

Answer Details

The time taken for the sound to travel from the boy to the cliff and back to the boy (i.e., the time for the echo) is 0.9s. Since the sound has to travel twice the distance between the boy and the cliff, we can use the formula:
distance = (speed of sound × time taken) ÷ 2
Plugging in the given values, we get:
distance = (330 × 0.9) ÷ 2 = 148.5m
Therefore, the boy should stand at a distance of 148.5m from the cliff to hear the echo of his clap 0.9s later. The correct option is (c) 148.50m.