Even when rain is falling vertically downwards the front screen of a moving car gets wet. On the other hand, the back screen remains dry. Why?
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Solution
Relative velocity:
We know that velocity is a vector and thus has a magnitude as well as a direction. Consider a parked car with rain falling on it. Because the vehicle is stationary, whatever direction the rain falls in will only hit the car from that direction.
Put it simply, if the rain falls vertically downwards, the rear and front ends of the car will get wet at the same time and in the same way, because the car is at rest in relation to the rain.
When the car starts moving, it acquires its own velocity component and direction in a horizontal direction, whereas the rain falls vertically downwards.
This direction difference would result in a velocity direction, which would be responsible for the droplets on the car.
This velocity direction points towards the car from the front, so the front screen gets wet first, followed by the back screen after some time.
