# Homework Help: Question about (the correctness or incorrectness) of a particular Energy formulation

1. Dec 7, 2009

### snnmbr

1. The problem statement, all variables and given/known data

Hi, I've been thinking about a formulation regarding "physical quantities" (that is, the quantities that specifically constitute the object of measurement for Physics), energy, and the conservation of energy. It would be very helpful for me that you could confirm me the thing is mathematically right, so here it goes (I just want to know if what I'm going to formulate is a compatible and correct, no matter if ugly or beautiful, mathematical expression about physical quantities, energy, and conservation of energy):

Let " Pq1 " be the "Physical quantity 1" (a certain physical quantity of a certain kind). So we'll have the physical quantities Pq1 , Pq2 , Pq3, ... , Pqn.

Now I am wondering: "in which ways could these physical quantities vary?", that is, "what combinations or configurations of values would be acceptable for Pq1 , Pq2 , Pq3, ... , Pqn "?

------------------------

2. Relevant equations

To anwer to this: 1º Step) I introduce "Energy", in a way :

Energy ( Pq1 , Pq2 , Pq3, ... , Pqn ) = Energy​

(Notice that, in this case, "Energy" is being the only physical quantity that is not following the notation Pqi ; but this is unimportant).

------------------------------

3. The attempt at a solution

... and, finally, 2º Step): I establish the set of equations: The space Pqi can support any configuration so that...

Energy ( Pq1 , Pq2 , Pq3, ... , Pqn ) = Energy

Energy = Constant​

(Or, in short, Pqi can assume any combination of values so that Energy ( Pq1 , Pq2 , Pq3, ... , Pqn ) = Constant )

Is this concept right? and if it is not, what would be the correction?

Thank you very much !!

2. Dec 7, 2009

### AEM

Re: Question about (the correctness or incorrectness) of a particular Energy formulat

You should read a good introductory physics book. There is no physical content in your expressions. You cannot just write symbols down and have it make sense. Physical quantities have units and meaning.

3. Dec 7, 2009

### snnmbr

Re: Question about (the correctness or incorrectness) of a particular Energy formulat

(Op here. Additional note to my opening post in case it could help someone:

Later I realized the suggested model is simply an easy variant of a Lagrangian.

Perfect illustrating example: a pendulus. Energy (position, velocity) = -Energy (position) + Energy (velocity) = constant.

Other thing: the constant character of Energy value has to do with up to 2 important things: 1º) conservation of energy; and 2º) minimization of energy (or principle of least action).

Bests.)

Last edited: Dec 7, 2009