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Phys101 Term:123 Online HW-Ch08-Lec02 Q1: A Block of mass m = 5.00 kg is released form rest from point A and slides on the frictionless track shown in figure. Determine the block’s speed at points B and C: A. B. C. D. E. vB vB vB vB vB = 5.94 m/s, v c = 7.67 m/s = 2.14 m/s, v c = 1.62 m/s = 1.84 m/s, v c = 3.47 m/s = 9.19 m/s, v c = 10.0 m/s = 9.19 m/s, v c = 15.0 m/s Ans: A; 1 2 mvB 2 + mgyB = 1 2 mvA 2 + mgyA ⇒ vB = �vA 2 + 2g(yA − yB ) = 5.94 m/s vc = �vA 2 + 2g(yA − yC ) = 7.67 m/s Q2: In Figure, a 3.5 kg block is accelerated from rest by compressed spring of spring constant 640 N/m. The block leaves the spring at the spring’s relaxed length and then travels over horizontal floor with a coefficient of kinetic friction u k = 0.25. The frictional force stops the block in distance D = 7.8 m. What is the original compression distance of the spring? Ans: ∆K + ∆U + ∆E+n = 0 1 (k f − k i ) + (Uf − Ui ) + µk mgD − kx 2 + +µk mgD = 0 2 2µk mgd ⇒x= � = 0.46 m k KFUPM-Physics Department 1 Phys101 Q3: Term:123 Online HW-Ch08-Lec02 A 4.0 kg bundle starts up a 30ᵒ incline with 128 J of kinetic energy. How far will it slide up the incline if the coefficient of kinetic friction between bundle and incline is 0.30? Ans: ∆K + ∆U + ∆E+n = 0 (k f − k i ) + (Uf − Ui ) + µk mgcosθd = 0 −k i + Uf + µk mgcosθd = 0 −k i + mgh + µk mgcosθd = 0 −k i + mgdsinθ + µk mgcosθd = 0 ⇒d= h 30ᵒ h = d sinθ ki = 4.3 m mg(sinθ + µk cosθ) KFUPM-Physics Department 2