Potential Energy system of 3 charged particles

  • #1

Main Question or Discussion Point

I simply can't wrap my head around a test question I received.

I'll relate it as best as I can remember:

"A system of 3 charged particles are arranged such that the total potential energy of the system is -200 J.
Then, consider the same 3 particles, arranged so that the potential energy of the system is -20 J.

Has the potential energy of the system decreased, increased, or stayed the same?"



The answer was : the potential energy increases


Let me explain why I'm stuck. Here's what I understand.

I understand that the number -200 is smaller than -20. If you look at it like that, then the answer is the energy of the system has increased.

But Potential energy = the ability to do work.

Considering that definition, the first system has the greater ability to do work, and thus has the higher potential energy, in which case the going from the first to the second system is a decrease in the ability to do work, and is therefore a decrease in the potential energy.

Your help is greatly appreciated, this question blindsided me and I feel like the timeline of my learning is on hold until I can overcome this hurdle!
 
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Answers and Replies

  • #2
Doc Al
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Considering that definition, the first system has the greater ability to do work, and thus has the higher potential energy,
Why do you say that?
 
  • #3
I don't know! haha

Both Work and Potential Energy are scalars. So a higher magnitude in potential energy represents a higher ability to do work.

no?
 
  • #4
Doc Al
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No. Just because something is a scalar does not mean that its sign can be ignored.
 
  • #5
I figured it out.

Thanks for the friendly and helpful response! :tongue:

Without your disparagement, no progress was possible!
 
  • #6
Doc Al
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