Work done on block by spring and friction

AI Thread Summary
The discussion revolves around calculating the work done on a block by a spring and friction as it moves from point A to point B. The block has a mass of 2.7 kg, the spring's force constant is 480 N/m, and the coefficient of kinetic friction is 0.18. The calculations for work done by the spring and friction yield values of 0.096 J and -0.0953532 J, respectively. However, there is confusion regarding the sign of the work done by the spring, which was initially marked incorrect but later accepted when changed to negative. The key takeaway is that while the spring's work depends solely on the positions, the friction's work is path-dependent, necessitating careful consideration of the distance over which friction acts.
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Homework Statement



In the system shown in the figure, suppose the block has a mass of 2.7 kg, the spring has a force constant of 480 N/m, and the coefficient of kinetic friction between the block and the floor is 0.18.

Find the work done on the block by the spring and by friction as the block is moved from point A to point B along path 2.

Diagram:
http://img706.imageshack.us/img706/5935/walker4ech08pr006.jpg

Homework Equations



Wspring = 1/2kx^2
Wfriction = -uk*m*g*x

The Attempt at a Solution



Wspring = 1/2(480)(0.020)^2 = 0.096
Wfriction = -(0.18)(2.7)(9.81)(0.020) = -0.0953532

I inserted these values into the system, but it said that my sign for Wspring is wrong, so I switched it to a negative. It stopped saying anything about my signs, but it won't say that it is correct. I'm not sure what is wrong...
THANKS.
 
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Although the work done by the spring only depends on the initial and final positions, the work done by friction depends on the entire path taken---i.e. what's the distance during which friction does work?
 
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