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 k 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 2 The figure below shows a block of mass M2 4 kg on a frictionless plane inclined at angle 40 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 M1 M2 40 a b c 3 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 B R A a b c 4 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 h 2m B C d 7m a b Formula sheet v v0 at r r0 v0 t 0 5a t 2 2 2 0 v v 2a x x0 PHY 2048 I I COM Mh 2 p mv F ext F ext M a COM Fs kx 1 R COM M I sphere m i ri tot 1 Wnet K I r F rF Wnet U s r E K U 0 t E K U Eth at r K rot K tot M 1 I 2 1 mv 2 Rv rel Ma v f v i v rel ln E mec K U r dm tot V 2 U y mgy U x 1 2 kx 2 I m ir 1 K mv 2 2 i I r 2 dm 2 2 mR 2 5 i R COM Eth f k d 1 mR 2 I cylinder 2 I ring mR 2 d 2 R COM dt 2 a COM v ac r v2 r 2 r I disk F m a 2 ar dp dt 2 1 I 2 2 Mi Mf
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