Question

why do we fall in the forward direction if a moving bus stops suddenly and fall in the backward direction if it suddenly accelerates from rest

Answer 1

When the bus moves suddenly our lower part of the body is in motion while the upper part is at rest .
When the bus stops our lower part of the body changes to rest first while upper part is still at motion
. So we move fore front while in a bus

Answer 2

Hii...
Due to the phenomena of moment of inertia we resist the opposite force by displacing..

In first case we move forward due to inertia of motion..as we hav a tendency to move in forward direction even after the bus stops..

In second case..we hav the tendency to remain in stationary place...so inertia of rest acts ...we move in opposite direction to force applied i.e backward..

hope this helps!