A body falls for 5s from rest. If the acceleration due to gravity of the earth ceases to act, the distance it travels in the next 3s is:

Initially, the body starts its motion from rest, so u = 0 m/s.

When acceleration due to gravity acts on the body for 5 s,  the velocity of the body after 5 s is given by 

v = u + at
$\Rightarrow$v = 0 + 9.8 x 5 = 49 m/s 

When acceleration stops acting, the velocity of the body is 49 m/s. The distance traveled by the body in next 3 s is given by -

$\mathrm{s}=\mathrm{ut}+\frac{1}{2}{\mathrm{at}}^2$

$\Rightarrow \mathrm{s}=49\times 3+(\frac{1}{2}\times 0\times {\mathrm{t}}^2)$

$=49 \times 3=147$ m