MP Board · Class 9 · Science · MotionA bus decreases its speed from $80\text{ km/h}$ to $60\text{ km/h}$ in $5\text{ s}$. Find the acceleration of the bus.

Given data:\nInitial velocity, $u = 80\text{ km/h} = 80 \times \frac{5}{18}\text{ m/s} = \frac{200}{9}\text{ m/s} \approx 22.22\text{ m/s}$\nFinal velocity, $v = 60\text{ km/h} = 60 \times \frac{5}{18}\text{ m/s} = \frac{150}{9}\text{ m/s} \approx 16.67\text{ m/s}$\nTime interval, $t = 5\text{ s}$ \nUsing the formula for acceleration $a = \frac{v - u}{t}$: $$a = \frac{16.67 - 22.22}{5} = \frac{-5.55}{5} = -1.11\text{ m/s}^2$$\nThus, the acceleration of the bus is $-1.11\text{ m/s}^2$. The negative sign indicates retardation.