PHYS 211 Lecture 14 Outline of Current Lecture I. FrictionII. Friction Practice ProblemsCurrent LectureI. Friction Always opposes direction of motionTypes of frictionStatic (μs): when the frictional force is large enough to prevent motionKinetic (μk): when two surfaces are sliding along each otherRolling friction: When an object is rolling without slippingII. Friction Practice ProblemsA 70 kg filing cabinet needs to be slid across a floor if the static coefficient of friction is 0.5 and the kinetic coefficient is 0.4, how hard to you have to push to move it at a constant velocity?Y: ∑F = FnetN-mg = maN = mg = (70kg)(9.8m/s2) X: ∑F = FnetFp- F = maFp = fFk = μkN = (.4)(686N) = 274 NFs = μsN = (.5)(680N) = 343 NYou need to push with 343 N to get it started and then contuinue to push at 274 N to keep it moving.If you are sledding on a hill with a slope of 30 degrees with a constant velocity, what is the coefficient of friction?Y: ∑F = FnetN-mgcosθ = maN = mgcosθThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.X: ∑F = FnetMgsinθ –fk = maMgsinθ = fkMk = sinθ/cosθ = OH/AH = tanθMk = tan30 =
View Full Document
Unlocking...