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gibson:teaching:fall-2013:math445:lecture21 [2013/12/03 05:48] gibson created |
gibson:teaching:fall-2013:math445:lecture21 [2013/12/03 05:50] (current) gibson [Physics] |
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Pendulum physics, F = ma with linear air resistance | Pendulum physics, F = ma with linear air resistance | ||
- | m l theta'' = -mg sin theta - b theta' | + | <latex> |
+ | m l \theta'' = -mg sin \theta - b \theta' | ||
- | theta'' + c theta' + g/l sin theta = 0 | + | \theta'' + c \theta' + g/l \sin \theta = 0 |
+ | </latex> | ||
This is a 2nd-order nonlinear differential equation in one variable, theta. | This is a 2nd-order nonlinear differential equation in one variable, theta. | ||
- | 2nd order b/c theta'' term. Nonlinear b/c sin theta. Linearization for small | + | 2nd order b/c $\theta''$ term. Nonlinear b/c $\sin \theta$. Linearization for small |
- | theta would approximate sin theta = theta for small theta. No big thing | + | theta would approximate sin theta = theta for small $\theta$. No big thing |
=====Get ODE into Matlab form===== | =====Get ODE into Matlab form===== | ||
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to a 1st order ODE in n variables, as follows. Let | to a 1st order ODE in n variables, as follows. Let | ||
+ | <latex> | ||
x1 = theta | x1 = theta | ||
x2 = theta' | x2 = theta' | ||
+ | </latex> | ||
Then | Then |