Question

a boy standing at a distance of 660m from acliff creates asound and hear the echo . if the speed of sound in air is 330m/s after what time will hear the echoes​

Answer 1

GiveN :-

• A boy standing at a distance of 660m from acliff creates asound and hear the echo .
• The speed to sound is 330 m/s .

To FinD :-

• The time after which echo will be heard .

SolutioN :-

Here the speed to sound in the medium is 330 m/s . And the distance of boy from cliff is 660 m .When a boy will produce a sound then the sound has to travel first to the cliff and then back from cliff to the boy . In this it will travel twice the distance between the boy and the cliff .

★ We know that :-

$\sf:\implies \pink{ Distance = Speed \times Time }\\\\\sf:\implies Time =\dfrac{Distance}{Speed} \\\\\sf:\implies t =\dfrac{ 660 m \times 2 }{330 m/s } \\\\\sf:\implies t = 2 \times 2 s \\\\\sf:\implies \underset{\blue{\sf Required \ Time}}{\underbrace{\boxed{\pink{\frak{ Time = 4 \ seconds }}}}}$

Answer 2

Given

• Distance (d) = 660 m
• Speed of sound (v) = 330 m/s

To find

• Time (t)

Solution

• Speed = Distance / Time
• Time = Distance / Speed
• Time = 660 × 2 / 330

Since, sound travels twice, first the sound travels to the cliff and then from the cliff to the boy.

• Time = 1320 / 330
• Time = 4

Hence, the time taken by the boy to hear the echoes is 4 s