Is delta_sc the distance from A to B in a straight line? If so, I am not getting the right answer for the problem. Also, does the angle of P have an affect on that term?
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Fall 2008 -- Purdue University -- West Lafayette, IN
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6 comments:
delta_ac is not in a straight line. You have to account for the x and y component of P and the distance traveled in each direction to find the work done by that force (this is the non-conservative term). Work done in the x-direction is positvie and in the y-direction is negative since the force is opposing the direction of motion.
you also have to include the force of gravity, which will actually make the work done in the y-direction positive.
In the work equation, does weight always act in the neg. j direction?
The non-conservative term only includes the applied force. The force of gravity is accounted for in the V (potential energy) equation. So you do not include the force of gravity in your U_nc term.
has anybody noticed that the problems are assigned in a section that doesn't even talk about Potential Energy until the next section...i know it gets the right answer but I'm just saying that were technically using something that "hasn't been taught" yet. Any comments?
David brings up a good point. You may include conservative forces (such as gravitational forces and spring forces) as EITHER a work term OR in the potential term, but NOT BOTH.
The particular section from which the problems come for this assignment has not yet introduced potential energy. However, we covered potential briefly in the 8:30 and 3:30 sections, and possibly in the 11:30 section. Feel free to use either approach with these problems.
The figure that I added to to Greg's original post illustrates on the work due to the applied force F. If you choose to include the gravitational force in work, use the same procedure. With this term, you have only a component of force in the negative y-direction.
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