As shown in the diagram, a block of mass m , released from rest at the top of an
ID: 1903544 • Letter: A
Question
As shown in the diagram, a block of mass m , released from rest at the top of an incline, slides down a length s from a height h down to the ground. The coefficient of kinetic friction between the plank and the barrel is ?k . a) Derive an expression for the work done by the force of friction on the block, as it slides down a distance s. b) Derive an expression for the work done by the force of gravity on the block, as it slides down a distance s. c) Using the Work-Energy theorem, derive an expression for the change in kinetic energy of the block, between the beginning and end of its slide. Digram: http://www.colorado.edu/physics/phys2010/phys2010_fa12/writtenhomework.htmlExplanation / Answer
assuming the incline does not move,
work done by friction = ND
= k X mgcos X s
cos = sqrt( 1- [h/s]^2 )
W.= k mg s( sqrt( 1- [h/s]^2 ) )
work done by gravity = mgh
chang in Ke =
mgh - W = 1/2mv^2
W= work done by friction.
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