A person driving a car suddenly applies the brakes on seeing a child on the road ahead. If he is not wearing seat belt, he falls forward and hits his head against the steering wheel. Why?
Due to inertia of motion, if a person applies breaks suddenly, then that person’s lower part slows down rapidly, but the upper part continues to move in the same direction and with the same speed & thus he/she ends up hitting his/her head against the steering wheel of the car.