Question

Why do you fall in the forward direction when a moving bus brakes to stop and fall backwards when it accelerates from rest?

Answer 1

Its due to a condition called inertia.When you are sitting,your body is ate rest.when the bus starts moving suddenly,you tend to move backward because of your body"s resistance to sudden movement.the same applies to the forward movement of your body

Answer 2

It is because of inertia.
The First Law Of Motion describes that : An object continues to be in a state of rest or of uniform motion along a straight line unless acted upon by an unbalanced force.
Inertia means the tendency of undisturbed objects to stay at rest or keep moving with the same velocity.
Thus when a moving bus brakes or accelerates our body resists to it, as a result it either moves forward or backward.