A driven pendulum

PHYSICS · Multi-part · Fermi University Physics · Mechanics & Dynamical Systems · Nonlinear dynamics and chaos · Nonlinear dynamics and chaos

Modes, Packets and Media, Ch Driven and pumped nonlinear oscillators and the route to chaos

Problem

A driven pendulum, sampled once per drive period (a stroboscopic section), settles into a period-three orbit: the strobe shows exactly three distinct points, and the trajectory exactly repeats after three drive periods. The drive angular frequency is ωd=0.900 rad s−1\omega_d = 0.900\,\text{rad s}^{-1}. ((a)) List, in ascending order, the angular frequencies (up to and including ωd\omega_d) at which this motion can show spectral lines. ((b)) State why a period-three orbit cannot show a line at ωd/2\omega_d/2.

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