Question

A person standing between two vertical cliffs and is 640 m away from the nearest cliff. He shouted and heard the first echo after 4s and the second echo after further 3s. Calculate the speed of sound in air and the distance between the cliffs.

Answer 1

Given:

d₁ = 640m

t₁ = 4s
t₂ = 4 + 3 = 7
First echo is heard from the nearest cliff.
Total distance travelled = 2d

= 2 × 640

= 1280 m
v = `(2"d"_1)/"t"_1`

=`1280/4`

= 320 m/s
Second echo is heard from the first cliff
v = `(2"d"_2)/"t"_2`

= `("2d"_2)/7`
d₂ = `(320xx7)/2`

= 1120 m
hence, the distance between two cliff
d₁ + d₂

= 640 + 1120

= 1760 m.