Potential Energy: Differentiating to Find Force

[omarMihilmy]

To find the force we will differentiate the function with respect to x (dx)
My problem is with the solution
If we differentiate:
dU/dx = 9x^2 - 7

From where does the negative come from also the j component?

 

[voko]

You should have used the homework template, then you have written the relevant equations. What equation is relevant for finding force from potential energy?

 

[omarMihilmy]

F = dU/dx

 

[voko]

That is not correct.

 

[omarMihilmy]

Correct me if I am wrong

 

[shanname]

Why are you disregarding the y-component when you differentiate?