Question

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A stone is falling freely from the rest and the total distance covered by it in the last second of its motion equals the distance covered by it in the first 3 seconds of its motion .How long does the stone remain in air ?

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Answer 1

ANSWER

s =ut + 0.5gt

2

_________1

In first 3sec, let it covers distance "d" m.

d=0.5g(3)

2

=4.5g

This distance is same as distance traveled in last second

So, according to formula,

S

n

=u+0.5a(2n−1)

4.5g=0.5g(2n−1)

Here, u=0 and n is number of seconds for which stone is in air.

∴n=5 sec

Substituting in eqn 1,

S= 122.5m

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