Contact Friction Forces: Force of Static Friction fs m mg Force of Kinetic Friction v N F fk m mg

Coefficients Of Friction Steel on steel 0.74 0.57 Aluminum on steel 0.61 0.47 Copper on steel 0.53 0.36 Rubber on concrete 1.0 0.8 Wood on wood 0.25-0.5 0.2 Glass on glass 0.94 0.4 Waxed wood on wet snow 0.14 0.1 Waxed wood on dry snow ------ 0.04 Metal on metal (lubricated) 0.15 0.06 Ice on ice 0.1 0.03 Teflon on Teflon 0.04 0.04

A man drags a m kg crate at constant speed across a floor by pulling on a rope inclined at q degrees above the horizontal. The tension in the rope is T N. Find the magnitude of the a) normal force exerted on the crate by the floor. b) frictional force acting on the crate. c) coefficient of kinetic friction between the crate and floor. mk N T q m fk Algebra! mg

y N F N mk F q f q m f x mg mg Pulling a block with constant speed The coefficient of friction The normal force The frictional force

m = 200 kg vo= 20 m/s ms = 0.500 Crate on truck A flatbed truck traveling at 20 m/s is carrying a 200 kg crate of heavy machinery - which is NOT tied down... The coefficient of static friction between the crate and the bed of the truck is 0.500. The driver applies the brakes and brings the truck to rest as quickly as possible without the crate sliding, find the: a) The maximum magnitude of the trucks deceleration when coming to a stop? b) distance traveled during the acceleration?