When a moving bus brakes, you tend to fall forward due to inertia of motion, while when it accelerates from rest, you tend to fall backward due to inertia of rest. Inertia is the tendency of an object to resist changes in its state of motion, whether that’s moving or staying still.
Forward Fall (Braking):
When the bus brakes, the lower part of your body (feet, legs) comes to a stop with the bus.
However, your upper body, due to inertia, continues to move forward at the bus’s previous speed.
This difference in motion causes you to lean forward.
Backward Fall (Acceleration):
When the bus accelerates from rest, your lower body starts moving forward with the bus.
Your upper body, due to inertia of rest, resists this change in motion and tends to stay at rest.
This resistance causes you to lean backward.