Question 5
How does a seat belt protect a passenger when the brakes are applied?
The right answer is the one marked above.
It applies a force to the upper body too, so the whole body stays at the car's velocity. Without a belt, only the lower half is stopped.
The belt does not stop the passenger sooner than the car — what it does is stop them at the same rate the car stops.
Without one, the body stops only when it meets the windscreen — that is, in a very short time. The same change in velocity over a shorter time means a bigger retardation, and so a bigger force.