Q. A body is released from the top of a tower of height H m. After 2s it is stopped and then instantaneously released. What will be its height after next 2s (in metres)?

(a) H-5

(b) H-10

(c) H-20

(d) H-40

Ans: (d)

Sol:

In first 2 sec

$\displaystyle h = 0+ \frac{1}{2} g 2^2 $

h = 20m

Again motion starts from rest

$\displaystyle h’ = 0+ \frac{1}{2}g 2^2$

h’ = 20m

Height after next 2 sec

= H-40