To determine the driver's momentum after the impact, we need to consider the fact that the driver was wearing a seatbelt. The seatbelt acts as a restraint, preventing the driver from being ejected from the car upon impact. Therefore, we can assume that the driver's velocity immediately after impact is approximately equal to zero.
Momentum is defined as the product of mass and velocity. Since the driver's velocity is assumed to be zero after impact, the driver's momentum after impact is effectively zero. This means that the driver's body has no net motion, and its position within the car remains unchanged.
