Which of the following affects friction?

Question 11 options:



the smoothness of the surfaces that are touching



the amount of force that is pressing objects together



both a and b



none of the above
May you also answer this one too!!

Engine oil reduces friction between the moving parts of a car engine by?
Question 12 options:


cooling the car engine


making the parts sticky so they will move slower


making the parts slippery so they will move by each other easier


none of the above
Thanks!!