Question 3
A passenger stands in a moving bus holding on to nothing. When the brakes are applied suddenly, which way do they fall, and why?
The right answer is the one marked above.
Forwards; because the upper body keeps the velocity it had. The feet were in contact with the bus, so the bus applies a force to them and brings them to rest.
But no such force is applied to the upper part of the body, so by the first law it carries on forwards at the velocity it already had. The lower half stops while the upper half goes on, so the passenger falls forwards.
The bus does not push the upper body forwards — the real reason is that no force acts on it at all.