Practice Problem

Sample problem – How much force is needed to push a 1.50 kg object down a 10° incline at 3.00 m/s² if µ = 0.1?

	Fdown – Fup = ma
	FA + F// – FF = ma
	FA + mg sin θ – µmg cos θ = ma

F_A + (1.5) (9.8) (sin 10) – (.1) (1.5) (9.8) (cos 10) = (1.5) (3)

FA + 2.5 – 1.4 = 4.5           FA = 3.4 N down (2 s.f.)

Practice problem -How much force is needed to push a 5.0 kg object up a 30° hill at a constant speed if µ = 0.2?

	Fup – Fdown = ma
	FA – F// – FF = ma
	FA – mg sin θ – µmg cos θ = ma

F_A – (5) (9.8) (sin 30) – (.2) (5) (9.8) (cos 30) = (5)(0)

F_A – 24.5 – 8.53 = 0          F_A = 3.3 × 10¹ N up