34. 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

34. 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

(a)  12sec

(b)  8sec

(c)  15sec

(d)  10sec

Answer :  (d)  10sec

t = \(\frac{d}{v}\) = \(\frac{150}{5}\) = 30 s     if train was stationary.

\( V_{Pt} = V_p - V_t \)

\( = -5 - (+10) \)

\( = -15\,\text{m/s} \)

t = \(\frac{d}{v_{pt}}\) = \(\frac{-150}{-15}\) = 10 s