Question

A moving train is brought to rest within $20second$ by applying brakes. Find the initial velocity if the relardation due to brakes is $2\mathrm{m}/{\mathrm{s}}^2$.

Answer 1

Assumptions:

Let initial velocity be$=um/s$

Step 1: Given Data:

Retardation of train,$a=-2m/s^2$

Time taken to stop the train,$t=20sec$

The final velocity of train, $v=0m/s$

Step 2: calculation:

As we know the rate of change of velocity is known as acceleration, so

$$\begin{gathered} Acceleration/retardation=\frac{v-u}{t} \\ -2m/s^2=\frac{0-u}{20sec} \\ u=20\times 2=40m/s \end{gathered}$$

Hence, the initial velocity of the train will be,$=40m/s$