Question

A stone falling from the top of a tower covers half of its height in the last second of its motion, the total height is
(a)57m. (b)27m.
(c)47m. (d)37m.​

Answer 1

ANSWER --A

Let the total time taken to hit the ground be t

Distance covered in nth second is given by H=12a(2n−1)

It covered half of the height, then

H2=12g(2t−1)

Also, it is under free fall, so total distance covered is,

H=12gt2

Equating the values of H that we got in the two cases above, we get

12gt2=g(2t−1)

t2−4t+2=0

t=2+2–√=3.4 or t=2−2–√=0.58

I'm using the first one,

H=12g(3.42)≈57m

Answer 2

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