How does friction impact work done by gravity on an inclined plane?

[kxk010]

Homework Statement

In a lab experiment, we pushed a cart up an inclined plane. The cart had wheels and we are taking friction into account. I'm told to describe both qualitatively and quantitatively the work done by force of gravity on way up track and then once again for back down. I also have to compare this with the force of friction.

Homework Equations

Work by gravity = -Ugravity = -Fd

The Attempt at a Solution

I'm just having trouble putting this into words. Can anyone help?

 

[jbsteele]

The work done by the force of gravity on the cart up the inclined plane is a negative value since gravity is acting against the motion of the cart. Quantitatively, the work done by the force of gravity can be calculated as the product of the magnitude of the gravitational force, F, and the displacement, d, of the cart along the inclined plane: Wgravity = -Fd. The force of friction also does work on the cart, but this work is positive since it acts in the same direction as the motion of the cart. The work done by friction is calculated similarly as Wfriction = Fd. Since gravity and friction are acting in opposite directions, the total work done on the cart is the difference between the work done by gravity and the work done by friction.For the cart going down the inclined plane, the work done by the force of gravity is still negative, since gravity is still acting against the motion of the cart. However, the work done by the force of friction is now negative, since it is acting against the motion of the cart. The total work done on the cart is the sum of the work done by gravity and the work done by friction.