Hello(adsbygoogle = window.adsbygoogle || []).push({});

Maybe I am standing on a garden hose (great German adage, does it exist in english or are you confused what I am talking about?)

Okay, to the topic:

Just for one dimension. It is easier:

We have [tex] m\ddot{x} = F(x(t)) [/tex] Now my book tells me that if I expansion with the velocity I should get:

[tex] \frac{m}{2} \frac{d}{dt} \dot{x}^{2} = - \frac{d}{dt} U(x(t)) [/tex]

I don't understand. Sadly I learnet it a year ago and I forgot everything. How sad a fate! :-(

I understand the right-hand side. Force is the derivative of the potential, the field must be conservative. But I dont understand the left-hand side.

1.) why is there a two under the mass?

2.) I expansion with the velocity? the differentialoperator on the velocity is my acceleration and the second velocity is one from the expansion. Where is the second? I could only identify one velocity. What happend?

Thanks

greetings

**Physics Forums | Science Articles, Homework Help, Discussion**

Dismiss Notice

Join Physics Forums Today!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

# Basics about Newtons law

**Physics Forums | Science Articles, Homework Help, Discussion**