Question

A boy standing some distance from the foot of a tall cliff claps his hands and hears an echo 0.5s later. If the speed of sound is 340 m/s, how far is he from the cliff?

a) 17m
b) 34m
c) 85m
d) 170m

Answer 1

To find the distance to the cliff, the time taken for the echo to return (0.5 seconds) is halved and multiplied by the speed of sound (340 m/s), resulting in a distance of 85 meters.

Step-by-step explanation:

The question involves calculating the distance between a boy and a cliff based on the time it takes for an echo to return and the known speed of sound. An echo occurs when a sound wave bounces off an object and travels back to the original source. Here, the echo takes 0.5 seconds to return after the boy claps his hands. Since the sound wave has to travel to the cliff and back, the time should be divided by 2 to find the time taken for the journey to the cliff. The distance can then be found by multiplying the time taken to reach the cliff by the speed of sound.

The calculation would be as follows:

1. Time for one-way journey: 0.5 seconds / 2 = 0.25 seconds.
2. Distance to the cliff: 0.25 seconds * 340 m/s = 85 meters.

Therefore, the correct answer is (c) 85 meters, as this is the distance the sound traveled to reach the cliff before returning as an echo.