Do you mean JERK?
When a driver suddenly applies the brakes, the car decelerates rapidly, but your body continues moving forward due to inertia, the tendency of objects to maintain their state of motion. This forward movement happens because your body is not directly attached to the vehicle’s braking system. As a result, you experience a jerk as your body lags behind the car's sudden stop. This phenomenon is a basic principle of physics that explains how forces affect motion.
One of the possible causes of a Pontiac Bonneville to jerk during acceleration is that the car needs a tune up. The engine misfiring can lead it to jerk as you accelerate.
When an elevator starts or stops, there is a change in acceleration which causes a shift in forces acting on your body. This sudden change can make you feel a jerk as your body adjusts to the new motion. It's similar to the sensation you feel when a car accelerates or decelerates quickly.
Poor driver or bad transmission.
Cylinder miss.
What causes a car to jerk while driving can be based on many factors. A car can sputter due to engine compression issues, bad transmission, engine misfire, bad spark plugs or even low fuel.
Inertia
When car was moving, passengers were also moving. When car suddenly stops, the moving passengers try to maintain their state of forward motion because of their inertia. so they move forward relative to their seats...
The force that causes the car to stop by opposing its motion is friction. Friction occurs between the tires of the car and the road surface, creating a force that resists the motion of the car, ultimately bringing it to a stop.
Because a body in motion tends to stay in motion. See the link, The Car and The Wall.
Slippage in the transmission or a bad torque converter