Conservative Force: Work Done and Potential Energy Calculation

In summary: But if you're doing AP Physics, you should have seen partial derivatives before.In summary, the conversation discusses finding the work done by a force and determining if it is a conservative force. The solution involves using partial derivatives and setting them equal to each other. The concept of partial derivatives is commonly covered in Calculus 2.
  • #1
daivinhtran
68
0

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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  • #2
Solution : dFx/dy = 3x^2y^2 = dFy/dx

Can someone explain me the derivative technique? I don't know they get these...
 
  • #3
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)
 
  • #4
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?
 
  • #5
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)
 
  • #6
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.
 
  • #7
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??
 
  • #8
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.
 

What is a conservative force?

A conservative force is a type of force that does not dissipate energy as it moves an object. This means that the work done by a conservative force is independent of the path taken by the object and only depends on the initial and final positions of the object.

What are some examples of conservative forces?

Some examples of conservative forces include gravity, electric forces, and magnetic forces. These forces can be represented by a potential energy function and follow the law of conservation of energy.

How are conservative forces different from non-conservative forces?

Unlike conservative forces, non-conservative forces dissipate energy as they move an object. This means that the work done by a non-conservative force is dependent on the path taken by the object and not just the initial and final positions.

What is the relationship between conservative forces and potential energy?

Conservative forces and potential energy are closely related. The potential energy of an object in a conservative force field is equal to the negative of the work done by the force to move the object from a reference point to its current position.

How can understanding conservative forces be useful in science and engineering?

Understanding conservative forces is essential in many areas of science and engineering. It allows for the calculation of potential energy and the prediction of an object's motion in a conservative force field. This knowledge is crucial in areas such as designing efficient machines and predicting the behavior of objects in space.

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