Question

While approaching a cliff in a car, a man fires a gun from a distance of 0.335 km. If the velocity of the car is 5m/s. When and where will the echo be heard by the man? (Take velocity of sound as 330m/s)
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Answer 1

Answer:

2.5 sec here a echo at 3 sec

Explanation:

Let the distance of the cliff from the initial position of the man be d m.

So, the distance traveled by sound in 3 sec=2d m

So, speed of sound, S=

Time

Distance

​

S=

3

2d

​

.....(i)

On moving closer to the cliff by a distance of 82.5 m, the distance=2(d−82.5) m

So,

S=

t

d

​

S=

2.5

2(d−82.5)

​

=

2.5

2d−2×82.5

​

.....(ii)

Therefore form equation (i) and (ii)

3

2d

​

=

2.5

2d−2×82.5

​

5d=6d−495

d=495 m

Thus it is the distance of the cliff from the initial position of the man.

Now,

S=

3

2×495

​

=330 m/s