Question

You are sitting in a stopped bus. When the bus starts moving forward, you appear to move backward relative to the bus. Which statement best explains this observation?

a
The motion of the bus creates an unbalanced backward force on you.
b
The bus moves forward, while inertia keeps you in place.
c
Inertia prevents the force of the bus from acting on you.
d
The force of inertia on you balances the force from the motion of the bus.

Answer 1

Answer: b

Explanation: When the bus accelerates forward your body tends to remain at its previous state of motion (at rest) because of inertia (Newton's 1st law). The bus moves forward under you, so relative to the bus you appear to move backward. There is no unbalanced backward force acting on you — instead the bus must push forward on you to accelerate you.