EasyPhysicsHigh School (11–12)Mechanics › GravitationMechanics › Work, Energy and PowerConceptualBoard Exam
Answer, and give a reason. Why is the gravitational potential energy of a satellite negative? …
Contributed by StemPy LabTry it on paper first. A hint, the key idea and the worked solution are here when you need them.
Answer, and give a reason.
- Why is the gravitational potential energy of a satellite negative?
- A satellite moves to a higher orbit. Does its potential energy rise or fall?
- Can the potential somewhere be zero while the field there is not?
Need a reminder? The key ideaShow
Taking zero far away: potential energy , potential . The work to move a body from to is , close to only for heights much smaller than . Near the Earth, .
The worked solution
Have you tried it?
Work it out on paper first. It is fine to get stuck or make a mistake: that is how we learn. When you are ready, go through the solution one step at a time, and check each step against your own.
Step 1. (a) Zero is chosen far away. Gravity pulls the satellite in, so it has less energy than when far: negative.
Step 2. (b) It rises (becomes less negative), toward zero.
Step 3. (c) Yes. Far from all masses the potential tends to zero while a weak field remains; and with several masses the potential can pass through any value where the field is not zero.
Answer: (a) Because of where zero is. (b) It rises. (c) Yes.
Watch out. The value of the potential is a choice; the field, its slope, is not.
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