Question

A person standing between two vertical cliffs and 480m from the nearest cliff shouts. He hears the first echo after 3s and the second echo 2s later. Calculate: 

1. The speed of sound. 

2. The distance of the other cliff from the person.

Answer 1

1. Let d₁ be the distance of the nearest cliff and d₂ be the distance of the farther cliff. The time for the first echo is t₁ = 3s The first echo will be heard from the nearest cliff. The total distance travelled by sound before reaching the person is 2d₁

Hence, the speed of sound is 320m/s.

2. The second echo is heard 2s after the first one. Hence, t₂ = 3 + 2 = 5s Again the sound travels a total distance 2d₂ before reaching the person. So, we get 

Hence, the distance between the other cliff and the person is 800 m.