Work done by friction on an incline plane

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Homework Help Overview

The discussion revolves around a block being pulled up and down an inclined plane, focusing on the work done by the rope and the effects of friction. The problem involves concepts from mechanics, particularly work, energy, and forces acting on an object on an incline.

Discussion Character

  • Exploratory, Conceptual clarification, Problem interpretation

Approaches and Questions Raised

  • Participants discuss the forces acting on the block, including tension, gravity, and friction. There are attempts to clarify the relationships between these forces and the work done by the rope. Questions about the appropriate equations and force diagrams are raised.

Discussion Status

Some participants have suggested starting with a force diagram to visualize the problem. There is an exploration of the forces involved, but no consensus has been reached on the specific equations or methods to apply.

Contextual Notes

Participants are considering the implications of pulling the block at a constant speed and the role of kinetic friction, as well as the need to verify relationships between work done and changes in energy.

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A block of mass M is being pulled up an inclined plane at a constant speed, by an attached rope that exerts a tension T. The block is pulled a distance L. The plane makes an angle θ with the horizontal, and the coefficient of kinetic friction between the block and the incline is μk.
a.) What is the work done by the rope?

b.) Find the total work done on the block, Wtot = Wcons + Wnoncons. Verify that Wtot = ΔKE.

Suppose that the rope is attached to the downward side of the block, and it is pulled down the plane, a distance L. The tension in the rope again has magnitude T. Assume once again that the sled is pulled at a constant speed.
a.) What is the work done by the rope?

b.)Verify that Wnon-cons = ΔPE + ΔKE by first calculating the change in kinetic energy.
I know work is equal to Force times the distance the object moved and that frictional force is equal to mgcos(theta)
 
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Start by drawing a force diagram.

What forces is the rope working against? Over what distance.
 
The tension force in the rope is working against the force of gravity as well as the force of friction on the block
 
So maybe if you reduce this to an equation ...?
 

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