WAEC - Physics (1988 - No. 31)
A boy standing a distance from the foot of a tall cliff claps his hands and hears an echo 0.5s later. If the speed of sound is 340ms1, how far is he from the cliff?
17m
34m
85m
170m
680m
解释
X = vt/2 = (340 x 0.5)/2 = 85m