# Internal energy present, is there conservation of energy?

1. Mar 7, 2009

### makeAwish

Hmm. This is another thing i'm unsure abt.

When some mechanical energy is converted to internal energy, can we still say that energy is conserved?
Can the internal energy be negative?

Thanks for answering my qns :)

2. Mar 8, 2009

### Mapes

You're going to need to be more specific. Yes, energy is always conserved.

Energy is always relative to a certain reference, so there's no problem with energy being negative.

3. Mar 8, 2009

### Phrak

Energy is always conserved, except when it isn't.

Energy is always conserved in the Classical Physics folder; not always conserved in others. :uhh:

4. Mar 8, 2009

### HallsofIvy

Staff Emeritus
Energy is always conserved in a "closed system"!

Of course, a "closed system" is defined as one in which energy is conserved!

5. Mar 8, 2009

### Phrak

So that's the difference between the folders.

Or is $$\partial_\mu p^\nu [/itex] folder covariant?, [tex]\frac{d}{df}\partial_\mu p^\nu = 0$$

Last edited: Mar 8, 2009