Rain falling vertically hits the windows of an intercity train which is travelling at 50m/s. A passenger watches the rain streaks on the window and estimates them to be an angle of 20 degrees to the horizontal.
(i) Calculate the speed the rain would run down a stationary window.
(ii) The train starts to slow down with a uniform deceleration and 1.5 minutes later the streaks are at 45 degrees to the horizontal. What is the deceleration of the train??
Could you draw a diagram , becuase it will help me.
Turn on thread page Beta
Another M1 vecotr help... watch
- Thread Starter
- 20-11-2005 16:17
- 20-11-2005 22:33
It doesn't look like M1 stuff, it's relative motion isn't it? Which exam board are you in?
Let be the velocity of the train and velocity of the rain respectively.
is vertically downwards, and is horizontal. Please draw a diagram for yourself.
i) So velocity of the rain respects to the train will be which makes an angle of 20 degrees with the horizontal.
-> tan20 = v/u -> v = utan20 (u, v without arrows are speeds)
ii) v = u'tan45 -> u' = v/tan45 = utan20/tan45
t = 1.5 mins = 90s
-> a = (u' - u)/t