Finding work done by friction on a box

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SUMMARY

The discussion centers on calculating the work done by friction on a box with a mass of 59.0 kg, pushed 83.0 m across a rough surface with an applied force of 204 N at a 30.0° angle. The coefficient of kinetic friction is 0.100. The user initially calculated the frictional force as 57.82 N using the equation Fƒ = μN, where N is the normal force. However, the user encountered an error in determining the work done by friction, which should be -4156.108 J, as the frictional force acts opposite to the direction of the applied force.

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A box of mass
m = 59.0 kg
(initially at rest) is pushed a distance
d = 83.0 m
across a rough warehouse floor by an applied force of
FA = 204 N
directed at an angle of 30.0° below the horizontal. The coefficient of kinetic friction between the floor and the box is 0.100. Determine the work done by the force of friction
7-p-001.gif


Homework Equations


W = fdcosΘ
Fƒ=μN

The Attempt at a Solution


I used the two above equations and I found that the applied force of friction would be 57.82 because that is .1*59*9.8 and then if you put that into the first equation, the work would be 57.82*83*cos30 which equals 4156.108 and then since it is opposite the applied force, it would be -4156.108. At least I thought. That's wrong and I don't know why. Please help!
 
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But in this problem, the normal force is larger than the weight.
 
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The vertical component of F add to weight.
Remember when resolving vector, here force, noted all the components. Here the X and Y components.
 

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