Question

A bus decreases its speed from 80 km/hr to 60 km/hr in 5 s. Find the acceleration of the bus.

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

Answer 1

The correct option is C

$-1.11m/s^2$

Initial speed, $u=80km/hr=80\times \frac{1000}{60\times 60}=\frac{800}{36}m/s$

Final speed, $v=60km/hr=60\times \frac{1000}{60\times 60}=\frac{600}{36}m/s$

Time taken, $t=5s$

Using, $v=u+at$,

Acceleration, $a=\frac{v-u}{t}=\frac{600-800}{36\times 5}=-1.11m/s^2$

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