Which of the following causes you to fall forward if you are standing in a moving bus, facing forward, and the bus comes to an immediate stop:
A. the force due to kinetic friction between you and the floor of the bus.
B. the normal force due to your contact with the floor of the bus.
C. the force due to static friction between you and the floor of the bus.
D. the force of gravity.
E. No forces were acting on you to cause you to fall.
The person is standing in a moving bus facing forwards. The bus comes to a sudden halt which causes the person to fall forward. The reason why this happens can be explained by Newton's First law of motion. An object at rest or moving at a constant velocity continues to do so unless it is acted upon by a force. When the person is moving in the bus the velocity of the person is constant. A sudden deceleration of the bus as it comes to a stop does not affect the person and he continues to moves at the constant velocity. In the absence of friction the person would slide on the floor and his motion would stop only when an obstacle is encountered.
This does not happen as there a force of friction acting between the person's feet and the floor of the bus. This does not allow the feet to continue to move freely though the person's body is not stopped in any way. The result is the person falling forward.
The person falls forward due to the force of static friction between him and the floor of the bus. The correct answer is option C.
C is not the correct answer. In my test it was marked wrong