Question

A boy is standing in front of a hill. The distance between him and the hill is 680 m. He shouts his name. If the speed of sound is 340m/s, what is the time after which he will hear the echo?

• A. 4 s
• B. 2 s
• C. 3 s
• D. 1 s

Answer 1

The correct option is A 4 s

The distance between the boy and the hill is 680m.
The speed of sound = 340m/s
$t=\frac{(2\times d)}{v}$
Where t is the time after which the boy will hear the echo,
d = distance between the boy and the hill
v = velocity of sound
On substituting the values we get,
$t=\frac{(2\times 680)}{340}$
$t=4s$
Hence, the boy will hear the echo after 4 s.