On what factors does friction depend?

How can we measure the force of friction between the block and the table?

Kinetic Friction < Static Friction Once an object gets moving, friction get’s less.

Regents Table of Coefficients of Friction

Example 1 Find the force of friction between a waxed ski sliding on snow when an 800 N skier is skiing horizontally. What if a skier half as heavy where on the same skis and snow?

Example 2: Downhill without friction (imaginary) If there were perfectly frictionless snow find the acceleration of an 800 N skier is skiing on a 30  slope. 800 Fy =800 cos30 = 692N = N N = -Fy Fx =800 sin30 = 400 N If W =800N = mg, then m = 80 kg Fnet = Fx = ma 400 = 80a so a = 5 m/s/s

Example 3: Downhill with friction Find the force of friction between a waxed ski sliding on snow when an 800 N skier is skiing on a 30  incline. Then find the skiers acceleration. 30 Fx =800 sin30 = 400 N Fnet = Fx – f = ma 800 Fy =800 cos30 = 692N = N N = -Fy N f W f=uN =.05 x 692 = 34N Fnet = 400– 31 = ma If W =800N = mg, then m = 80 kg Fnet = 369N = 80a, so a = 4.58 m/s/s