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