Motion in a Straight Line - Result Question 34
35. A train of 150 metre long is going towards north direction at a speed of $10 m / s$. A parrot flies at the speed of $5 m / s$ towards south direction parallel to the railway track. The time taken by the parrot to cross the train is
[1988]
Topic 4: Motion Under Gravity
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Answer:
Correct Answer: 35. (d)
Solution:
- (d) Relative velocity of parrot w.r.t the train $=10-(-5)=15 ms^{-1}$.
Time taken by parrot to cross the train
$=\frac{150}{15}=10 s$
When two bodies are moving in direction relative velocity is sum of individual velocities.
$ \vec{v} _{A B}= \vec{v} _A- \vec{v} _B $
The distance which bird has to travel to cross the train is equal to the length of train. Now since the train and the bird are travelling in opposite direction, therefore the speed will be added up.
