Question

In a crash testing at 40 [mi/h], why do occupants move in the forward direction in the opposite direction of the acceleration of the vehicle?

Answer 1

Occupants move in the forward direction in the opposite direction of the acceleration of the vehicle due to the inertia of motion. This is because the occupants is in state of motion in forward direction and the inertia of motion always opposes the change in the state of motion.