Work done by Friction on an Inclined Plane

AI Thread Summary
The discussion revolves around calculating the work done by friction on a suitcase being pulled up an inclined plane. The suitcase has a mass of 17.1 kg, and the force applied is 146 N with a coefficient of kinetic friction of 0.257. An initial attempt to calculate the friction force incorrectly used the formula for static friction, leading to confusion about the work done. After realizing the need to consider the normal force's dependence on gravity and the incline's angle, the correct approach was acknowledged. The conversation highlights the importance of free body diagrams in resolving forces on inclined planes.
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Homework Statement



A luggage handler pulls a suitcase of mass 17.1 kg up a ramp inclined at an angle 24.0 above the horizontal by a force of magnitude 146 N that acts parallel to the ramp. The coefficient of kinetic friction between the ramp and the incline is 0.257. The suitcase travels a distance 3.90 m along the ramp.

What is the work done on the suitcase by the friction force?

Homework Equations



W = F o r = |F|*|r|*cos(theta)
Friction Force = uN

The Attempt at a Solution



Ok so I calculated that the Friction Force should equal umg since the direction of movement is along the incline rather than in the x direction. So Friction Force = 43.06806 N. If we multiply it by the change in distance, the Work done by friction should be -168 J, but this doesn't seem to be the correct answer. Anyone know where I may have screwed up?
 
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well force of friction is not \mu mg . set up a free body diagram first.
 
Oh wow... I'm sorry that was a stupid move on my part. For some reason I forgot that the normal force depends on gravity AND the direction of the gravitational force... Thanks so much I appreciate it!
 
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