Question

A body starts from rest at time $t=0$, accelerates uniformly and travels $320m$ in $4s$. Find its velocity at time $t=10s$.

• A. $40m/s$
• B. $400m/s$
• C. $200m/s$
• D. $20m/s$

Answer 1

The correct option is B $400m/s$

Given:
Distance travelled, $s=320m$.
Time, $t=4s$
Initial velocity, $u=0$ (as the body starts from rest)

Using the equation of motion,
$s=ut+\frac{1}{2}a{t}^2$
$320=0+\frac{1}{2}\times a\times 4^2$
$a=\frac{320}{8}=40m/s^2$

So, velocity $v$ after $10s$ can be found by:
$v=u+at$
$v=0+40\times 10$
$v=400m/s$