Hi, thanks for replying.
I was taught that as an object is moved further away from the central body, it gains GPE (KE decreases). GPE will continue to increase to 0, at an infinite distance away.
Likewise, as the object falls to Earth, its GPE decreases and KE increases (goes faster).
Hi,
Sorry I meant to say "as an object is moved from infinity to a point". You are correct that as an object moves further from the central body it will gain GPE (less negative number) and decrease in KE. There are really 2 forms of the GPE equation, one is U = - GMm/r and the other is Ep = mgh which is used when an object is near the earths surface. Using the second equation, the textbook will be correct since it doesn't factor in the negative sign of the U = - GMm/r. Ep is sort of like a simplification of the U equation since we usually consider GPE on a smaller scale rather than the scale of the entire universe.
If the planet's surface is chosen at a zero level, Ep at x is positive.
If infinity is chosen at the zero level, Ep is negative.
This may be why the textbook says GPE increases.