Question

why do the passengers fall in backward direction when a bus suddenly starts moving from the rest position?​

Answer 1

Answer:

when the bus suddenly starts moving the lower part of the passenger's body begins to move along with the bus while the upper part tends to remain at rest due to the inertia of rest. That it is why a passenger standing or sitting loosely in a bus falls backward when the bus suddenly starts moving.

Answer 2

When the bus starts moving suddenly, the lower part of the body of passengers, which is in contact with the bus, come in motion, but upper part of their body tends to be in the state of rest and the passengers fall backward.