RobVG said:
W=F*D Work is measured in Joules. How the hell can D be irrelevant?
"You just made a mistake. "Newtons" is not a unit of energy.
Newtons is a unit of force, just like pounds (lbs)."
I was asking what "force" is required to lift the weight."
Well, the thing is (and I think this might be what caused the confusion), 500 lbs IS the force. The pound is a unit of force, not a unit of mass. In particular, 500 lbs is the
weight of the object, and its "weight" is defined as the force with which Earth's gravity pulls down on it. So...you already know the force.
You know the force, and you know the distance, so all you have to do is multiply these two numbers, and you'll arrive at your answer for the increase in potential energy. Now, since you want the answer in joules, which are Newton-metres, a metric unit, it's probably best if you first convert both the force and the distance to metric units. So, as russ suggested, all you have to do is look up the conversion factors between pounds and Newtons, and between metres and feet.
With his comment about the height being irrelevant, what russ was trying to get at was that if all you wanted know was the
force and not the GPE (which is what you implied in post #6), then the height was no longer required as a value in solving the problem. To get the force in Newtons, all you have to do is convert the 500 lbs of force to Newtons. I think that's all he was saying, and no rudeness was intended.
I strongly advise you to give this forum a chance. You'll find no better place for
accurate physics advice and help online. Please let me know if you need any further clarification!