The car's mass is 400 kg. It moves at a velocity of 20 m/s. Calculate the car's momentum. A.
8000 kg*m/s
B.
20 kg*m/s
C.
0.05 kg*m/s
D.
80,000 kg*m/s

490 n  f=125n a=2.5m/s2

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