If water is trapped between two planes on a train, and the train decelerates at 4ms^-2. What angle does the surface of the water make with the horizontal?
Draw a diagram of forces on a single particle at surface of water.
Water is stationary in reference to train, thus when including decelerating force, resulting force is zero.
Balance horrizontal and vertical components:
ma = Rsin(theta) (Horrizontal)
mg = Rcos(theta) (Vertical)
Divide on by the other:
tan(theta) = a/g
(a = 4 ms^-2)
theta = 22.18
OS