Question

A body starts accelerating from rest under gravity. What is the displacement of the body in the time interval of the 10-15 seconds? (Assume $g=10{ms}^{-2}$)

• A. 575 m
• B. 600 m
• C. 1000 m
• D. 625 m

Answer 1

The correct option is

D

625 m

Given, initial velocity, $u=0m{s}^{-1}$ and acceleration, $a=10m{s}^{-2}$
From the first equation of motion, we have, $v=u+at$
Velocity after 10 seconds is
$v=0+10\times 10$ $=100m{s}^{-1}$
Now we have to find the displacement between 10 to 15 seconds
In this case, initial velocity, $u=100m{s}^{-1}$
Time taken, $t=15-10=5s$

Let 's' be the displacement.
From the second equation of motion, we have,
$s=ut+\frac{1}{2}a{t}^2$
$\Rightarrow s=100\times 5+\frac{1}{2}\times 10\times 5^2$
$\Rightarrow s=500+125=625m$