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Question

# A body falls freely from the top of a tower. It covers 36% of the total height in the last second before striking the ground level. The height of the tower is

A
50 m
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B
75 m
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C
100 m
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D
125 m
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Solution

## The correct option is D 125 mLet the height of tower be h and the body takes time t to reach the ground when it falls freely. Using second equation of motion, we have h=ut+12gt2 (Take downward direction as positive) ⇒h=12gt2 (∵ u=0 during free fall) .…(i) In the last second, i.e., in tth second the body travels 0.36h. Thus, in |t−1| seconds, it travels h–0.36h=0.64h So, we get, 0.64h=12g(t−1)2 ....(ii) On solving equ. (i) and (ii), we get ⇒h0.64h=12gt212g(t−1)2⟹t=5 s Substituting in equation (i), h=125 m

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