Find the relative velocities of the following: two cars travelling North on the same road, one travelling
at 15 m/s the other travelling at 20 m/s

B) raising the temperature and reducing the volume of the gas.|-/ 

Sorry i don’t know what to do

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