Work and Energy just shits me. I created another topic because I think this topic warrants one.
Let up be positive.
If an object falls from a height of 10m, gravity does
of work to the object. That means the object
gains 100J of energy, right? But as a consequence, doesn't this mean that at a height of 10m, it doesn't actually have any energy?
Also, imagine lifting a book from the floor to a table 1m high at a constant rate. Gravity does
. Your hand does work against gravity equal to
. But doesn't this mean that
? But how can this be, seeing as the book now has gained 'gravitational potential energy'?
And finally, in one of the questions, someone is towed up a slide with frictional force 300N. The
total work done to bring them to the top of the slide is 22720J. The change in their GPE is 13720J. Does this mean that the object has an extra 9000J of energy if it was pushed up to the top instead of being lifted to the top? How can this be, if its start and end positions are the same?