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

Options

A. 6s
B. 7 s
C. 9 s
D. 10 s

Answer

B

Explanation

Relative velocity of bird w.r.t train= 25+30 m//s time taken by the bird to cross the train ` t=(210)/(30) =7 sec `