Question

A train of $150m$length Is going towards the north direction at a speed of $10m/s$. A parrot flying at the Speed of $5m/s$ towards south direction parallel to the railway track. The time taken by the parrot to cross the train is equal to

• A. 8s
• B. 10s
• C. 12s
• D. 15s

Answer 1

The correct option is B

10s

Step 1: Given:

1. A train of $150m$in length is going in the north direction at a speed of $10m/s$
2. A parrot flying at the speed of $5m/s$towards the south direction parallel to the railway track.

Step 2: The time required to cross the train is given by;

$$\begin{gathered} Time=\frac{Dis\tan ce}{Speed} \\ Here,dis\tan ce=lengthofthetrain \\ Time=\frac{Length}{Relativevelocity} \\ Relativevelocity=velocityoftrain-velocityofparrot \end{gathered}$$

Let's take the velocity of the train as positive then the parrot's velocity will be negative.

$Relativevelocity=10-(-5)=15m/s.$

Step 3: Finding the time:

So the time required to cross the train is given by
$Time=\frac{Length}{Relativevelocity}=\frac{150}{15}=10sec.$

Hence, the correct option is (B).