A student is sitting on the right side of a school bus when it makes a right turn. We know that the force of gravity acts downwards and a normal force from the seat acts upwards. If the student stays in place when the bus turns, we also know that there must be
A) no other force on the student.
B) a force parallel to the seat directed forward on the student.
C) a force parallel to the seat directed to the left on the student.
D) a force parallel to the seat directed to the right on the student.
E) a force parallel to the seat in a direction between forward and left on the student.

Question

Quizplus · Accepted Answer

When the bus turns right, the student experiences a change in direction, and according to Newton's first law, the student would continue moving in a straight line if there were no external forces acting on them. Therefore, to stay in place relative to the bus, there must be a force acting in the opposite direction of the turn. Since the turn is to the right, the force must be directed to the left. This force is provided by the frictional force between the student's body and the seat of the bus. This force is parallel to the seat and directed to the right, as indicated by choice D.

A Student Is Sitting on the Right Side of a School