Why Does ∫δWdt = -∫δVdt?

[Gloyn]

Hi!

In this paper:

http://www.atm.ox.ac.uk/user/read/mechanics/LA-notes.pdf

On the bottom of page no. 25 there is written, that:

\int δWdt=-\int δVdt. Why is that? Can anyone explain into me?

Thanks in advance.

 

[Gloyn]

Ok, got it, it's simply NII, force equals derivative of potential.