Question

You watch distant Sally Homemaker driving nails into a front porch at a regular rate of 1 stroke per second. You hear the sound of the blows exactly synchronized with the blows you see. And then you hear one more blow after you see the hammering stop. Explain how you calculate that Sally is 340 m away from you.?

Answer 1

The velocity of sound of an echo is given as:

v = 2d/t, where d is the distance the sound source and the reflecting surface.

The time take for the stroke to be heard is 2s, because the rate is one stoke per second(one stroke in 1s). It means it will be heard after 2s, after the reflection of the sound wave.

v is speed of sound in air(Value 240m/s)

Therefore, d = vt/2 = (340 x 2)/2

d = 340m.

Sally is 340m away.

Step-by-step explanation:

The above question is an application of echo.

Echo is a sound heard after the reflection of sound wave.

The distance covered will be twice the distance between the source of the sound and the reflecting surface. This is because the sound will travel a certain distance to a reflecting surface and travels back equal distance to the source after getting reflected.