Question

A 210 meter long train is moving due North at a of 25m/s. A small bird is flying due South a little above the train with speed 5m/s. The time taken by the bird to cross the train is

• A. $6s$
• B. $\mathbf{7s}$
• C. $9s$
• D. $10s$

Answer 1

Answer: (B)

$\mathbf{7s}$

Answer 2

Relative velocity of bird w.r.t train

$= 25 + 5 = 30\mspace{6mu} m/s$

time taken by the bird to cross the train