Solution to Classical Mechanics Problem: Removing Constant Terms

[rmfw]

Ayo everybody, I'm doing a problem about theory of small oscilatons (see pic) and I got the following for potential energy:

V= mg(\frac{l_{2}}{2} +\frac{l_{1}}{2} \theta^{2}_{1} + \frac{l_{2}}{4} \theta^{2}_{2}) (after the aproximation cos \theta~ 1 - \frac{\theta^{2}}{2}

Knowing that V = \frac{1}{2} V_{jk} \theta_{jk} I need to write the matrix V_{jk}

Since the term mg\frac{l_{2}}{2} is constant, can I remove it from the potential ?

And write the matrix like this:

V_{jk} =mg \begin{pmatrix}<br /> l_{1} &amp; 0 \\<br /> 0 &amp; \frac{l_{2}}{2} \\<br /> \end{pmatrix}<br />

If not, how can I remove the constant term?

 

[mfb]

Constant terms don't matter, you can ignore them. They just reflect the arbitrary choice of "zero height".