Question

when we sit any person last seat of bus it jumps a lot what is the reason

Answer 1

I think this is a riddle

Answer 2

This is a good question,
your answer is,

The back wheels are usually several feet further from the back of the bus.
So when going around bumps or corners , the rear of the bus swings with a greater arc.
Therefore, any sudden movements are amplified for passengers sitting in the back.