Question

A train of 150 m in length is going in the north direction at a speed of 10 $\frac{m}{s}$.A parrot flies at a speed of 5$\frac{m}{s}$towards the south direction parallel to the railway track. The time taken by the parrot to cross the train is equal to. In the above questions, if the parrot flies at a speed of 5$\frac{m}{s}$ towards the north. The time taken by the train to leave past the parrot is :

• A. 25 s
• B. 20 s
• C. 30 s
• D. 50 s

Answer 1

The correct option is C

30 s

Step 1: Given

Length of the train = 150 m.

Speed of train and parrot are in the same direction.

Speed of the parrot $V_{parrot}=5\frac{m}{s}.$

Speed of train $V_{train}=10\frac{m}{s}$

Step 2: Formula

Velocity of a parrot with respect to train is given by $V=V_p-V_t.$

$$\begin{gathered} Speed=\frac{Dis\tan ce}{time}. \\ Dis\tan ce=Speed\times time. \end{gathered}$$

Step 3: Calculation

The relative velocity of parrot with respect to train is $V=V_p-V_t.$

$V=V_p-V_t.$

V=(5 - 10) =-5 $\frac{m}{s}$.

Time taken by the parrot to cross the train =

$$\begin{gathered} \frac{150}{5}=30s. \\ t=30s. \end{gathered}$$

The time taken by the parrot to cross the train = 30 seconds.

Hence, option (C) is the correct answer.