Which GPE formula is right and when do I use this other

[zachdr1]

In my formula sheet I have written down that

deltaPEg = (PEg final - PEg initial)

but then I have written down that

-(deltaPEg) = (PEg final - PEg initial)

which one is right?

Oh and another question, when do I use the formula

deltaK + deltaPE = 0?

 

[mfb]

Depends on the sign convention you like for the energy difference.

Oh and another question, when do I use the formula

deltaK + deltaPE = 0?

When it is applicable and helps.

Physics is not about memorizing formulas, it is about understanding how to get the formulas needed to solve the problem.

 

[Dale]

While I agree with mfb, I do think that the convention for the $\Delta$ symbol is pretty standard. I would always use $\Delta f = f_{final}-f_{initial}$ for any and all $f$.

 

[Herman Trivilino]

Oh and another question, when do I use the formula

deltaK + deltaPE = 0?

When the total mechanical energy of a system is constant (conserved).