Confusion over potential energy equation.

[Kyle Barr]

Hi, I am confused over the potential energy equation. I have been taught that potential energy is MGH M=mass, G=gravity on surface, and H=height from earth. However being on the internet and learning more i have noticed people use GmM/r^2 and i am very confused why it is switched. please help me with my confusion? Thank you. (:

 

[Simon Bridge]

Welcome to PF,
the equation for gravitational potential energy you learned is an approximation that holds close to the surface of the Earth. The other one is more correct in general, though there should be no square on the bottom, but is a pain to use, so we only use it when we have to.
Consider... the word "height" does not make much sence for the distance from a sphere.

 

[Kyle Barr]

thank you very much! and i just realized it is + distance, not squared. i got confused with the force of gravity equation.