Question

A car moving at $2.5m{s}^{-1}$ doubles its velocity with an acceleration of $0.5m{s}^{-2}$ in some time. If the same car travels at $1.5m{s}^{-1}$, what will be its final velocity if same acceleration acts on it for same time?

• A. $2m{s}^{-1}$
• B. $3m{s}^{-1}$
• C. $4m{s}^{-1}$
• D. $5m{s}^{-1}$

Answer 1

Answer: (C)

$4m{s}^{-1}$

$u=2.5m{s}^{-1}$
$v=2u=5m{s}^{-1}$
$a=0.5m{s}^{-2}$
Let us use: $v=u+at$
or, $5=2.5+(0.5\times t)$
or, $t=\frac{2.5}{0.5}=5s$
So, using this value, but different initial velocity $u$ =$1.5m{s}^{-1}$ we get:

$v=u+at=1.5+(0.5\times 5)=4m{s}^{-1}$