Conservative Force: Work Done and Potential Energy Calculation

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Homework Help Overview

The discussion revolves around determining the work done by a force defined as F = ix^2y^3 + jx^3y^2, establishing whether this force is conservative, and finding the potential energy U(x, y). The subject area includes concepts from vector calculus and physics, particularly relating to conservative forces and potential energy.

Discussion Character

  • Conceptual clarification, Mathematical reasoning, Assumption checking

Approaches and Questions Raised

  • Participants explore the condition for a force to be conservative, specifically the relationship between the derivatives of its components. There are attempts to compute these derivatives, with some participants questioning the use of partial derivatives versus total derivatives. Others express uncertainty about the derivative techniques involved and seek clarification on the steps required to approach the problem.

Discussion Status

The discussion is ongoing, with participants providing insights into the nature of partial derivatives and their application in this context. Some guidance has been offered regarding the treatment of variables as constants during differentiation, but there is no explicit consensus on the methods or solutions being discussed.

Contextual Notes

Some participants express uncertainty about their educational background and whether the concepts discussed are covered in their curriculum, indicating a potential gap in foundational knowledge related to calculus and physics.

daivinhtran
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Homework Statement



Find the work done by a force F = ix^2y^3 + jx^3y^2
Show that this
is a conservative force and find the potential energy U(x, y).

Homework Equations


A force F is conservative when :
dFx/dy = dFy/dx


The Attempt at a Solution



dFx/dy = d(x^2y^3)/dy = (2xdx/dy)(y^3) + (x^2)(3y^2)
dFy/dx = d(x^3/y^2)dx = (3x^2)(y^2) + (x^3)(2ydy/dx)

They're not equivalent though
 
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Solution : dFx/dy = 3x^2y^2 = dFy/dx

Can someone explain me the derivative technique? I don't know they get these...
 
daivinhtran said:
A force F is conservative when :
dFx/dy = dFy/dx
Should be partial derivatives: ∂Fx/∂y = ∂Fy/∂x
dFx/dy = d(x^2y^3)/dy = (2xdx/dy)(y^3) + (x^2)(3y^2)
dFy/dx = d(x^3/y^2)dx = (3x^2)(y^2) + (x^3)(2ydy/dx)
They will be when you change to partial derivatives. (∂y/∂x = ∂x/∂y = 0)
 
haruspex said:
Should be partial derivatives: ∂Fx/∂y = ∂Fy/∂x

They will be when you change to partial derivatives. (∂y/∂x = ∂x/∂y = 0)

WHat do you mean partial ??

Can you or anyone show me just a first few steps?
 
I'm self studying AP Physics C in high school. Am I expected to know it? Are there any simpler way to solve it? ( My way is to integrate in different paths, but I"m not sure)
 
If you have a number of independent variables (in this case, x and y), and a function f of these, the partial derivative of f wrt x (written ∂f/∂x) means the change in f as x changes slightly but y stays constant. So when performing a partial derivative wrt x, treat y as a constant: ∂y/∂x = 0. Likewise ∂x/∂y = 0.
Plug those into the equation you got.
 
haruspex said:
If you have a number of independent variables (in this case, x and y), and a function f of these, the partial derivative of f wrt x (written ∂f/∂x) means the change in f as x changes slightly but y stays constant. So when performing a partial derivative wrt x, treat y as a constant: ∂y/∂x = 0. Likewise ∂x/∂y = 0.
Plug those into the equation you got.

Are those material in Calculus 2??
 
daivinhtran said:
Are those material in Calculus 2??
I don't know what education system you're in, let alone what's in what syllabus.
 

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