Which GPE formula is right and when do I use this other

  • Context: High School 
  • Thread starter Thread starter zachdr1
  • Start date Start date
  • Tags Tags
    Formula Gpe
Click For Summary

Discussion Overview

The discussion revolves around the correct formulation and application of gravitational potential energy (GPE) equations, specifically the differences in sign conventions and the conditions under which certain energy formulas are applicable. It includes theoretical considerations and conceptual clarifications regarding energy conservation in physics.

Discussion Character

  • Debate/contested
  • Conceptual clarification

Main Points Raised

  • One participant questions the correctness of two different expressions for gravitational potential energy change, suggesting a potential confusion over sign conventions.
  • Another participant notes that the choice of sign convention for energy differences is subjective and depends on personal preference.
  • A third participant asserts a standard convention for the delta symbol, stating that it should always represent the final value minus the initial value.
  • Multiple participants inquire about the conditions for using the formula deltaK + deltaPE = 0, with one suggesting it applies when total mechanical energy is conserved.

Areas of Agreement / Disagreement

Participants express differing views on the correct sign convention for energy differences, indicating a lack of consensus on which formula is "right." There are multiple competing perspectives on when to apply the energy conservation formula.

Contextual Notes

The discussion highlights potential limitations in understanding due to varying interpretations of the delta symbol and the conditions for energy conservation, which may depend on specific scenarios or definitions.

zachdr1
Messages
89
Reaction score
0
In my formula sheet I have written down that

deltaPEg = (PEg final - PEg initial)

but then I have written down that

-(deltaPEg) = (PEg final - PEg initial)

which one is right?

Oh and another question, when do I use the formula

deltaK + deltaPE = 0?
 
Physics news on Phys.org
Depends on the sign convention you like for the energy difference.

zachdr1 said:
Oh and another question, when do I use the formula

deltaK + deltaPE = 0?
When it is applicable and helps.

Physics is not about memorizing formulas, it is about understanding how to get the formulas needed to solve the problem.
 
While I agree with mfb, I do think that the convention for the ##\Delta## symbol is pretty standard. I would always use ##\Delta f = f_{final}-f_{initial}## for any and all ##f##.
 
zachdr1 said:
Oh and another question, when do I use the formula

deltaK + deltaPE = 0?

When the total mechanical energy of a system is constant (conserved).
 

Similar threads

  • · Replies 9 ·
Replies
9
Views
2K
  • · Replies 2 ·
Replies
2
Views
1K
  • · Replies 5 ·
Replies
5
Views
9K
  • · Replies 8 ·
Replies
8
Views
922
  • · Replies 9 ·
Replies
9
Views
4K
  • · Replies 29 ·
Replies
29
Views
2K
  • · Replies 23 ·
Replies
23
Views
3K
  • · Replies 5 ·
Replies
5
Views
3K
  • · Replies 11 ·
Replies
11
Views
2K
  • · Replies 27 ·
Replies
27
Views
5K