A race car starts from rest and is accelerated uniformly to 41 m/s in 8.0 s. What is the car’s displacement?

Hi, your answer is not correct. this is a cumulative  

The answer is as follows in the photo

Answer(a)   the matererials that are in contact, the two materials and the nature of their surfaces/// (b)/// the force pushing the two surfaces together, pushing the surfaces together causes the more of the asperities to come together and increases the surface area in contact with each other