Q.Wind is blowing in the north direction at a speed of 2 m/s which causes the rain to fall at some angle with the vertical. With what velocity should a cyclist drive so that the rain appears vertical to him?
A) 2m/s south
B) 2m/s north
C) 4m/s west
D) 4m/s south
This all has to do with relative perceptions. The wind is blowing due north at 2 meters per second during a rainfall. A person standing still on the ground will see that the rain is falling at an angle in the direction of the wind. But if a person is riding a bicycle also due north at a speed of 2 meters per second, then the person is travelling in the same direction and speed as the wind blowing the rain. So while the rain will be falling at an angle to an observer on the ground, the cyclist will have the same frame of reference as the rain and it will appear to be falling straight down. That is why the answer is B.