Question
Rain is falling vertically with a speed of 30 m s-1. A woman rides a bicycle with a speed of 10 m s-1 in the north to south direction. What is the direction in which she should hold her umbrella?
Solution
Let,
vc = Velocity of the cyclist, andvr = Velocity of falling rain
The woman must hold her umbrella in the direction of the relative velocity (v) of the rain, in order to protect herself from the rain.

Therefore, the woman must hold the umbrella towards the south, at an angle of 18o.