A Physics Question

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A physics student pulls a block of mass m = 25 kg up an incline at a slow constant velocity for a distance of? A physics student pulls a block of mass m = 25 kg up an incline at a slow constant velocity for a distance of d = 3 m. The incline makes an angle q = 28° with the horizontal. The coefficient of kinetic friction between the block and the inclined plane is µk = 0.4. a) What is the work Wm done by the student? Wm = J HELP: Draw a free-body diagram of the block. HELP: There are three forces acting on the block: the forces due to the string, gravity, and friction. Pay attention to the direction in which these forces are acting. Also, the statement that the block is pulled with constant velocity tells you something about the forces. What does this tell you? At the top of the incline, the string by which she was pulling the block breaks. The block, which was at rest, slides down a distance d = 3 m before it reaches a frictionless horizontal surface. A spring is mounted horizontally on the frictionless surface with one end attached to a wall. The block hits the spring, compresses it a distance L = 0.9 m, then rebounds back from the spring, retraces its path along the horizontal surface, and climbs up the incline. b) What is the speed v of the block when it first reaches the horizontal surface? v = m/s HELP: Use the work-energy theorem. HELP: What is the work done on the block by gravity? What is the work done on the block by friction? The sum of these two numbers will equal the kinetic energy of the block at the bottom of the incline. c) What is the spring constant k of the spring? k = N/m HELP: Use conservation of energy. HELP: When the spring is fully compressed, the speed of the block is zero and therefore the kinetic energy of the block is zero. All the energy must be stored in the spring. d) How far up the incline d1 does the block rebound? d1 = m HELP: REMEMBER: There is no friction on the horizontal surface, but there is still friction on the incline. HELP: Since there is no friction on the horizontal surface, the speed found in (b) must be the initial speed of the block as it rebounds up the incline.