Question

A pebble is dropped freely in a well from its top. It takes 20 s for the pebble to reach the water surface in the well. Taking g = 10 m s-2 and speed of sound = 330 m s-1. Find: (i) The depth of water surface and (ii) The time when echo is heard after the pebble is dropped.

Answer 1

Answer:

h=

2

1

×10×(20)

2

=5×400=2000m

Now, t

1

= time of falling =20sec

t

2

= time taken by sound

=

V

sonic

H

=

330

2000

=6.06s

∴ Time after dropping the pebble at which echo is heard =26.06sec

Explanation:

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