Question

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

• A. 2.22m/s²
• B. 2.11 m/s²
• C. 1.11 m/s²
• D. 0 m/s²

Answer 1

The correct option is C

1.11 m/s²

Initial speed $\left(u\right)=80\frac{km}{hr}=80\times \frac{1000}{60\times 60}=\frac{800m}{36s}$

Final speed $\left(v\right)=60\frac{km}{hr}=60\times \frac{1000}{60\times 60}=\frac{600m}{36s}$

Time taken $\left(t\right)=5s$

$a=\frac{v-u}{t}$ $=\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. So, the deceleration is $1.11m/s^2$.