Question 4
A passenger stands in a stationary bus. It is started without their noticing and pulls away forwards. Which way do they fall?
The right answer is the one marked above.
Backwards; because the upper body is still at rest. As the motion begins, the bus applies a force to the feet in contact with it, so the lower part of the body gains a velocity.
But no force acts on the upper part, so it stays at rest. The lower half moves off while the upper half stays put, and the passenger is pushed backwards.
Braking and pulling away, the upper body does the same one thing — carrying on exactly as it was. The direction of the fall reverses because what the bus does reverses.