# Finding force from torque equation

I have read an article on electrostatics textbook that, $$\vec {F}= \nabla {\vec {\tau} }$$ Such as,the toraue equation on a magnetic dipole is $$\vec\tau={\frac{{\mu}_0 m^2}{2\pi z^3} }\hat{z}$$ The the force on this dipole is $$\vec{F}=-{\frac{{3\mu}_0 m^2}{2\pi z^4} } \hat {z}$$ Can anyone help me proving this?

• Is that supposed to be the curl? Because the gradient of a vector is generally a dyad (a tensor) and divergence a scalar – Kyle Kanos Mar 12 at 15:28
• Where did you read this, in particular? – probably_someone Mar 12 at 15:28