Question

How does a diffuser or spoiler affect the cars momentum and what are its benefits.

Answer 1

Diffuser or spoiler in the car body has a function as an airplane wing. it generates a lift to the body as well as a drag force, so a ratio of lift/drag has to be optimized. These structures increases grip on the road without increasing the weight of the body, and hence the car bodies stick to road.And hence the drag force and lift force would not decrease the momentum of the car as compared to the case if optimised. It increase friction and increase fuel efficiency also.

thus it has a positive effect on momentum of car and increase it.