Question

A bus decreases its speed from $80km{h}^{-1}$ to $60km{h}^{-1}$ in $5s$, find the acceleration of the bus.

Answer 1

Step 1: Given data

Initial velocity, $u=80km{h}^{-1}=22.2m{s}^{-1}$

Final velocity, $v=60km{h}^{-1}=16.7m{s}^{-1}$

Time, $t=5s$

Step 2: Formula used

$v=u+at$

Where “a” is the acceleration.

Step 3: Determine the acceleration

Using the first equation of motion,

$$\begin{gathered} v=u+at \\ 16.7=22.2+a\left(5\right) \\ a=\frac{16.7-22.2}{5} \\ a=-1.1m{s}^{-2} \end{gathered}$$

The value is negative as the bus is decelerating

Therefore, the acceleration of the bus is $-1.1m{s}^{-2}$