A stone is dropped into a lake from a tower 500 meter high. The sound

| A stone is dropped into a lake from a tower 500 meter high. The sound of splash will be heard by the man approximately after:

A. 11.5 sec

B. 21 sec

C. 10 sec

D. 14 sec

Right Answer is: A

SOLUTION

We know that

s = ut +1 /2 at²

here u = 0, a = g, s = 500m

so putting value in the above equation

500 = 0 + 5t²
t²=100
t=10 s 

we get t = 10s. this is the time taken for stone to hit the lake.

Now

Velocity of sound in air 332m/s

time of sound travel = t

Distance= sound ×time

500 = 332 × t

t = 1.5 sec

total time = 10+1.5 = 11.5s.

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