Solving Two Hours of Christmas Arguing: PE on a Cliff and Ramp?

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Discussion Overview

The discussion revolves around the concept of gravitational potential energy (PE) in different scenarios involving objects at the same height but varying contexts, such as standing on a cliff versus being inside a box on a ramp. Participants explore how the presence of additional factors might influence the potential energy calculations.

Discussion Character

  • Exploratory
  • Debate/contested
  • Conceptual clarification

Main Points Raised

  • One participant questions whether a man at the edge of a cliff has the same potential energy as a man at the same height but further away from the cliff, suggesting that height relative to a reference point is key.
  • Another participant agrees that if two equal masses are at the same height, they have the same potential energy, regardless of their distance from the cliff.
  • Discussion arises about whether placing an object on the edge of a ramp inside an immovable box affects its potential energy, with one participant stating that if the box is massless, it does not change the PE.
  • Another participant introduces the idea that if the box has a non-negligible mass, it could alter the potential energy of the object on the ramp.
  • One participant emphasizes the importance of not complicating the scenario with unnecessary factors that may not significantly affect the outcome.
  • A later reply predicts that the dispute may remain unresolved due to differing views on the relevance of additional factors in the scenarios presented.

Areas of Agreement / Disagreement

Participants generally agree that potential energy is determined by height relative to a reference point, but there is disagreement on the impact of additional factors, such as the mass of the box, on potential energy calculations. The discussion remains unresolved regarding the influence of these factors.

Contextual Notes

Participants express uncertainty about how to handle factors like the mass of the box and its gravitational effects, indicating that assumptions about these elements may significantly influence the discussion.

jimprince
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Simple Question??

Here is a question I argued with my family for over two hours Christmas evening...
If a man is standing on the edge of a plateau overlooking a 1000' cliff, does he have the SAME potential energy of a man of the same mass at the same elevation on the plateau but 2 miles from the cliff?
Now, what if you put an object on the edge of a ramp, does it have the same PE as an object of the same mass on the edge of the ramp but inside of an immovable box? Would the box change the PE?
We have an "airline ticket to Florida" wager on this argument so any details would be appreciated.
Thanks!
 
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PS: Our reference point is the bottom of the cliff.
 
Near the Earth's surface, the gravitational PE is just mgh: it just depends on the height with respect to some arbitrary reference point. So, ignoring any trivial differences in g from place to place, if two equal masses have the same height then they have the same PE.
jimprince said:
If a man is standing on the edge of a plateau overlooking a 1000' cliff, does he have the SAME potential energy of a man of the same mass at the same elevation on the plateau but 2 miles from the cliff?
Sure, why not?
Now, what if you put an object on the edge of a ramp, does it have the same PE as an object of the same mass on the edge of the ramp but inside of an immovable box? Would the box change the PE?
Makes no difference.
 
Now, what if you put an object on the edge of a ramp, does it have the same PE as an object of the same mass on the edge of the ramp but inside of an immovable box? Would the box change the PE?
If the box is assumed to be massless (or at least of negligible mass), then there would be no change in PE. Otherwise, the box could be contrived to have its own, non-negligible gravitational field, in which case the potential energy of the object on the ramp would change.

Barring such an odd situation, there would be no change in the PE of the box.
 
You shouldn't add more than the strictly needed factors. At least not when they hardly makes a difference.
 
I predict that you will not be able to resolve the dispute due to an inability to agree on how irrelevant factors being added to the scenario confuse and change the actual scenario.
 

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