A train is travelling at vm//s along a level straight track Very near and parallel to the track is a wall On the wall a naughty boy has drawn a straight line that slopes upward at a `37^(@)` angle with the horizontal A passanger in the train is observing the line out of window (`0.90` m high `1.8` wide as shown in figure) The line first appears at window corner A and finally disappears at window corner B if it takes `0.4` sec between appearance at A and disappearance of the line at B what is the value of v (in cm//s)?

Answer

`750`

Explanation

`h/(vt-l)=tan 37^(@)`
Rightarrow v=`h(+l)/((tan 37^(@)/t)) = 7.5 m//s =750 cm//s]`