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## Homework Statement

http://www.webassign.net/userimages/jlabelle@dartmouth/graph.gif

A block with mass m = 10 kg slides along a horizontal floor. The kinetic friction force opposing the motion of the block is constant at a value 14 N. At clock reading t=0.0 s and position x=0.0 m, the block has an instantaneous velocity of v = 4 m/s to the right. A force P is applied to the block starting at the instant it is in the position x=0. The direction of P remains fixed and positive (to the right), but its magnitude varies according to the graph above. Use work and energy arguments to answer the questions below; do not make use of Newton's second law.

a) Calculate the work done by the force P in the displacement from x=0 to x=4 m.

b) Calculate the work done by the frictional force during the same displacement

c) Calculate the work done by the net force acting on the block during the displacement.

d) Calculate the change in kinetic energy of the block.

e) Calculate the final kinetic energy of the block; that is, the kinetic energy it possesses on reaching the position x=4 m.

f) Calculate the velocity of the block at the position x=4 m.

g) Calculate how far the block will slide beyond position x=4 m if the force P abruptly drops to zero at this position and remains zero from there on.

h) Calculate any potential energy changes of the earth-block system that take place over the course of the motion from x=0 to x=4 m.

## Homework Equations

## The Attempt at a Solution

a) I found the area under the curve = 100 J

b) 14N*4m*cos180 = -56 J

c or d, I am not sure which) 100J+(-56J) = 44 J

I am not sure about the rest. Can someone help me out??

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