Question

You are on a train that is traveling at 3.0 m/s along a level straight track. Very near and parallel to the track is a wall that slopes upward at a 12° angle with the horizontal. As you face the window (0.86 m high, 2.1 m wide) in your compartment, the train is moving to the left, as the drawing indicates. The top edge of the wall first appears at window corner A and eventually disappears at window corner B. How much time passes between appearance and disappearance of the upper edge of the wall?

Answer 1

Can some one answer this question i really dont know how to solve it either

Answer 2

Find time for edge of corner A to appear if train moves at 3 m/s: 
t = d/v = 2.0m/3.0m/s = 0.67s after edge appears at A

Then find the distance for the train to travel in order for the wall to rise 0.90m (the height of the window) by using trigonometry. 
Tan 12 degrees = 0.90m/D   
D = 4.23m

At 3m/s, it will take the train 1.41s to travel 4.23m. (4.23m/ (3m/s) = 1.41s)

The total time = (time for edge A to appear) + (time to travel the length of the wall)
Total time = 0.67s + 1.41s = 2.08s = 2.1s