# B Equation dealing with energy?

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1. Dec 5, 2017

### kburkus

What is
ΔEp = ΔEk + W
I have come across this formula, but i haven't seen it before. What is it used for?

2. Dec 5, 2017

### Merlin3189

Δ is used to mean a change in something, so
Change in Ep = Change in Ek + W

Beyond that I'm stuck unless the person who composed the formula tells me.

I could guess the E stood for energy and the subscripts p and k stood for potential and kinetic.
W might then stand for work.

But that is a total guess, since formulae are made up by people according to their own mathematical needs. An equation or formula without context has no definite physical meaning.

Edit 3. Oh, you asked about use. If it is something like the meaning I guessed, then you might use it to calculate changes in potential energy and kinetic energy when work is done on a body. But you'd have to be very careful to measure the variables suitably, as this formula would not take account of the signs of the quantities. A better formula to use might be ΔPE = W - ΔKE

(edits 1& 2 were typographical)

Last edited: Dec 5, 2017
3. Dec 5, 2017

### Merlin3189

And there you go! I guessed wrong. Try looking at laws of Thermodynamics. That seems to be the context where formulae using these symbols occur when I search in Google.

Sorry to have it wrong.

Lets hope Chestermiller, is around. He's a whizz on thermodynamics.