A soldier walks toward a high wall making 120 steps per minute.When he is at a distance of 85cm from the wall,he observes that the echo of a step coincides with the next step.The speed of sound isa)85m/s b)170m/s c)980m/s d)exactly 340m/s

Open in App

Solution

Total no. of steps in one second = 120/60 = 2

Total distance travelled by the sound wave in round trip = 85×2 cm = 170 cm

when echo previous step is coincide with the next step then time interval is 1/2 = 0.5 s
( because 2 steps are covered in 1 second so one step will be covered in 1/2 s)

Speed of the sound = distance travelled / time taken = 170/0.5 = 340 cm/s

Suggest Corrections

Similar questions

Q. A boy stands facing a high wall at a distance of 85 m from it and then blows a whistle. Calculate the time interval when he hears an echo (Speed of sound = 340 m

s^{- 1}

A person is standing at a distance of $d m$ from a wall and clapping at a rate of $4$ claps per second. The echo of his clap coincides with his clap and he hears the echo of two claps after he stops clapping. What is $d$ ? (Assume velocity of sound to be $340 m / s$ )

Q. A man fired a bullet against a wall and hears an echo after 2 s. He walks 80 m towards the wall and fired bullet, such that he hears echo after 1 s. Find the distance from wall to the second fired place.

Q. A boy is walking away from a well at a speed of 1.0 m/s in a direction at right angles to the wall. As he walks, he blows a whistle steadily. An observer towards whom the boy is walking hears 4.0 beats per second. If the speed of sound is 340 m/s, what is the frequency of the whistle(in Hz)?

Q. A boy is walking away from a wall at a speed of 1m/s in a direction at right angle to the wall. As he walks, he blows a whistle steadily. An observer towards whom the boy is walking hears 4 beats per second. If the speed of sound is 340m/s, what is the frequency of the whistle?

Join BYJU'S Learning Program