Question

A bus decreases its speed from $80kmph$ to $60kmph$ in 5 seconds. Find the acceleration of the bus.

• A. $2.22m{s}^{-2}$
• B. $2.11m{s}^{-2}$
• C. $1.11m{s}^{-2}$
• D. 0

Answer 1

The correct option is C

$1.11m{s}^{-2}$

Initial speed, $u=80kmph$ = $80\times \frac{1000}{60\times 60}=\frac{800}{36}m{s}^{-1}$

Final speed, $v=60kmph$ = $60\times \frac{1000}{60\times 60}=\frac{600}{36}m{s}^{-1}$

Time taken $t=5s$
From the first equation of motion,
$a=\frac{v-u}{t}$ $=\frac{600-800}{36\times 5}$$=-1.11m{s}^{-2}$.

Here sign of acceleration is negative which shows that the speed is decreasing and acceleration is in the opposite direction of the motion.