# Work, Velocity & Force vectors Help

1. Sep 13, 2010

### Jonnyb42

This is probably more of a math question, but it pertains to physics.

Today in Classical Mechanics the professor was showing the following,

F . dr = (MV2^2)/2 - (MV1^2)/2

but in great length, one of the steps along the way I did not understand how he did it... it was this:

screw latex, if someone could please post a link to somewhere on the forums that shows how to use latex properly, I can't use it to save my life...
here is the step with good old microsoft:

[PLAIN]http://mynqa.com/Cargo/unk.bmp [Broken]

My questions are, where did the number 2 come from in the denominator? Also, how did he bring in the velocity vector into the derivative like that?

Thanks for any help.

Last edited by a moderator: May 4, 2017
2. Sep 14, 2010

### gabbagabbahey

See my sig

Just apply the product rule to the right-hand side of the equation...

Last edited by a moderator: May 4, 2017
3. Sep 14, 2010

### mathman

It is essentially the vector equivalent of the derivative of a square.

d/dt(x2)=2xdx/dt