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

When a moving bus brakes to a stop, the lower part of your body, which is in contact with the bus, stops as the bus slows down. However, the upper part of your body tends to continue moving forward due to inertia—the tendency of a body to resist changes in its state of motion. This results in you falling forward. Conversely, when the bus accelerates from rest, the lower part of your body moves forward with the bus, but the upper part initially remains at rest due to inertia. As a result, you fall backward until your entire body starts moving with the bus. This behavior is explained by the principle of inertia, which states that an object in motion tends to stay in motion, and an object at rest tends to stay at rest unless acted upon by an external force. The difference in motion between the lower and upper parts of your body as the bus changes speed causes the forward or backward falling sensation.