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← JEE Main 2017 · 8 Apr · Shift 1
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JEE Main 2017 · 8 Apr · Shift 1, Physics question 4

An object is dropped from a height h from the ground. Every time it hits the ground it looses 50% of its kinetic energy. The total distance covered as t→∞t\to\infty is :

Choose one option
Answer and worked solution

Official answer: C

The official answer, 53h\frac53h, corresponds to the speed being halved at each bounce (e=12e=\frac12, so each rebound height is 14\frac14 of the previous one):
d=h+2(h4+h16+… )=h+2h/41−1/4=53h.d=h+2\left(\frac h4+\frac h{16}+\dots\right)=h+\frac{2h/4}{1-1/4}=\frac53h.
Read literally, losing 50% of the kinetic energy makes each rebound height 12\frac12 of the previous, which gives h+2h=3hh+2h=3h, not among the options. The answer follows the official key.