The following pairs of surfaces are pushed together with the same amount of force. Between which pair of surfaces will friction be the greatest?
A. two pieces of sandpaper
B. two pieces of waxed paper
C. a painted surface and a piece of sandpaper
D. a painted surface and a piece of waxed paper


Juan and his friends want to build their own go-karts and race down their street. According to Newton’s Second Law of Motion, which of these will help Juan to win the race?
A. increasing the mass of his go-kart
B. increasing the amount of inertia the go-kart has
C. decreasing the net force applied to the go-kart
D. decreasing the mass of his go-kart