Lesson Plan

Distinguish static friction from kinetic friction and state when each acts

Apply f_s ≤ μ_s N, f_s(max) = μ_s N, and f_k = μ_k N to compute friction forces

Resolve an object's weight into components parallel and perpendicular to an inclined plane

Find the normal force and the acceleration of an object on an incline, with and without friction

Use the constant-velocity slide condition μ_k = tan θ to determine a coefficient of kinetic friction

5.4

"When there is no motion between the objects, the magnitude of static friction f_s is f_s ≤ μ_s N ... this equation says that static friction can have a maximum value of μ_s N. ... Once an object is moving, the magnitude of kinetic friction f_k is given by f_k = μ_k N." "When an object rests on an incline that makes an angle θ with the horizontal, the force of gravity acting on the object is divided into two components: A force acting perpendicular to the plane, w_⊥, and a force acting parallel to the plane, w_∥. ... w_∥ = w sin(θ) = mg sin(θ) and w_⊥ = w cos(θ) = mg cos(θ)." "μ_k = (mg sin θ)/(mg cos θ) = tan θ."