Why does man sitting in bus gets an outward jerk when bus takes a sudden turn?

Answer 1

It is caused by Centrifugal Force. An example is a weight fastened on the end of a string. Twirl the string in a circle, and the weight flies outwards, constrained only by the length of the string. As the bus turns sharply, so passenger are forced outwards, like the weight on the end of the string. Obviously, most passenger resist the force and remain seated by leaning inwards, or grabbing the seat in front, etc. Any passenger not holding on, could be flung against the side of the bus, or thrown into the lap of any passenger seated nearby.

Answer 2

due to centrifugal force