The bus moves our
lower portion of the body,i.e., the legs go in motion along with the bus
as it is in direct contact with the floor of the bus. And simultaneously,
our upper body also comes in motion gradually.Thus our whole body comes in
motion. But when the bus stops, our legs which are in direct contact with the
bus, also stops but our upper body is still in motion.Thus our legs stop and
our body goes forward.This is the reason why we tend to lean forward when the moving
bus stops suddenly