Expression of the force derived from this potential

[Andrei0408]

Homework Statement:

Knowing that the potential is U = - α / r , where α is a positive constant and r the distance from the
potential field source, find the expression of the force deriving from this potential; Give examples of forces that derive from such a potential.

Relevant Equations:

Not sure

I just don't know what equations I should use, or what exactly I need to do. I just need some guidelines, thank you!

 

[Frigus]

I think this link may help you
http://labman.phys.utk.edu/phys135core/modules/m6/potential_energy.html

 

[Delta2]

It is a well known fact that given the potential function $U(r,\theta,\phi)$ of a field , the force that the field applies to a test point charge (or test point mass or whatever is the field subject)$q$ is given by $$\vec{F}=-q\nabla U$$.

So all you have to do is calculate the gradient $\nabla U$ of the function $U$. I assume from the context that the calculation must be done in spherical coordinates. So it will be $$\nabla U=\frac{\partial U}{\partial r}\hat r+\frac{1}{r}\frac{\partial U}{\partial \theta}\hat\theta+\frac{1}{r\sin\theta}\frac{\partial U}{\partial \phi}\hat\phi$$

Also note that in your case the function U does not depend on $\theta$ and $\phi$ so the above formula for the gradient of U simplifies a lot.