Dynamics - sled up a hill with several angles?

[optoracko]

Homework Statement

A boy drags his sled of 90.0N at a constant speed up a 18 degree hill. He pulls with a 40.0N force on a rope which is 35 degrees above the horizontal.

a) What is coefficient of kinetic friction between the sled and the snow?

Homework Equations

Coefficieint = Force of Kinetic Friction / Normal Force

The Attempt at a Solution

I can find the normal force, no problem. It's just the kinetic friction I'm having trouble finding. I would think that the kinetic friction would be whatever the x component of the force applied is, since that is what is opposing the sled. However, if that was true, the Force net of the x prime would be 0. How would this be the kinetic friction then? Wouldn't it be for static since there is no movement?

I thought of doing this and checked yahoo answers, a response had a similar method. I just don't understand why to do this though.

 

[JaWiB]

I'm not sure I understand. What is your coordinate system? Is the x-direction parallel to the slope, or parallel to the horizontal? What is x prime?

 

[optoracko]

I'm not sure I understand. What is your coordinate system? Is the x-direction parallel to the slope, or parallel to the horizontal? What is x prime?

The x direction is parallel to the slope. X basically the x direction (the slope, back and forth). Don't know why I said prime now, lol.

 

[JaWiB]

Ok, well first of all the x-component of the pulling force isn't equal to the friction force because gravity also has a component in the x-direction. Second, zero net force means zero acceleration, not necessarily no movement.