PHY 2048-S4, Fall 2009 Examination #2 October 20, 2009 Instructor: Beatriz Roldan Cuenya Name______________________________________ID______________ Please answer all questions. #1______________ #2______________ #3______________ #4______________ Total: ___________ Show all work and enter answers in boxes, if provided.1. A 0.2 kg block slides along an incline plane with coefficient of kinetic friction µk=0.2. (a) What should be the minimum angle of the incline in order to have the block slipping down? (b) If the angle of the incline plane is 30°, calculate the work done by the frictional force when the block slides down the incline a distance of 3 m. (c) What is the work done by the gravitational force during the 3-m downward displacement? (d) What is the minimum external force parallel to the surface of the incline plane that will start the block moving up the incline? Assume a 30° incline plane. (a) (b) (c) (d) α2. The figure below shows a block of mass M2 = 4 kg on a frictionless plane inclined at angle θ = 40º. It is connected by a cord of negligible mass to a block of mass M1= 1 kg on a horizontal frictionless surface. The pulley is frictionless and massless. Calculate: (a) Magnitude of the normal forces on each block. (b) Acceleration of the boxes. (c) Tension in the connecting cord. (a) (b) (c) M1 M2 40º3. A 1.5 kg stone attached to the end of a non-elastic cord describes a vertical circular trajectory of 2 m radius. When the stone is at its highest point, the tension in the cord TB =20 N. Calculate: (Use Newton second law and energetic considerations). (a) Magnitude of the stone’s velocity at B (b) Magnitude of the stone’s velocity at A (c) Tension on the cord at A. (a) (b) (c) B A R4. A block is released from rest at height h = 2m and slides down a frictionless ramp onto a plateau, which has a length d = 7 m and where the coefficient of kinetic friction is 0.4. (a)What is the block’s speed at the end of the incline plane (B)? (b)Can the block reach the plateau’s end (C)? If the block cannot reach C, how far from B will it stop? If it does, how far up the incline plane will it travel? (a) (b) h = 2 m d = 7 m A B CFormula sheet PHY 2048
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