1. The problem statement, all variables and given/known data I am just wondering what effect a torsional spring, with constant K, would have on the equations (1) to (5), under the section "Force analysis and system equations". The torsional spring is located where the pendulum and cart are connected http://ctms.engin.umich.edu/CTMS/index.php?example=InvertedPendulum§ion=SystemModeling 2. Relevant equations 3. The attempt at a solution I think it would only affect the moment equation, with an extra term K(theta)?