Question

A car moving with initial velocity of $10m{s}^{-1}$ attains a speed, v in 5 seconds. The car travels a distance of 100 m. Find v.

• A. $10m{s}^{-1}$
• B. $20m{s}^{-1}$
• C. $30m{s}^{-1}$
• D. $40m{s}^{-1}$

Answer 1

The correct option is C $30m{s}^{-1}$

Given,
initial velocity, $u=10m{s}^{-1}$
time taken, t = 5 s
distance covered, s = 100 m

Let the final velocity be 'v' and acceleration be 'a'.
From the second equation of motion,
$s=ut+\frac{1}{2}\times {at}^2$,
$100=10\times 5+\frac{1}{2}\times a\times 5^2$
$\therefore$$a=4m{s}^{-2}$
From the first equation of motion,
v = u + at,
$v=10+4\times 5$ = $30m{s}^{-1}$
Therefore the final velocity is $30m{s}^{-1}$.