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Simple harmonic motion
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<p>In <a href="/facts/Mechanics/A3yHLQA5">mechanics</a> and <a href="/facts/Physics/a7aH2y08">physics</a>, simple harmonic motion (sometimes abbreviated as SHM) is a special type of <a href="/facts/Periodic_function/Sm8lJQsF">periodic</a> <a href="/facts/Motion/dCnP7MlB">motion</a> an object experiences by means of a <a href="/facts/Restoring_force/8uT24jt6">restoring force</a> whose magnitude is directly <a href="/facts/Proportionality_(mathematics)/xDQmfh6t">proportional</a> to the distance of the object from an equilibrium position and acts towards the equilibrium position. It results in an <a href="/facts/Oscillation/6vSrm84a">oscillation</a> that is described by a <a href="/facts/Sinusoid/mD1CB09M">sinusoid</a> which continues indefinitely (if uninhibited by <a href="/facts/Friction/d0108Rpu">friction</a> or any other <a href="/facts/Dissipation/C134STy1">dissipation</a> of <a href="/facts/Energy/wd8PrQM7">energy</a>). </p><p>Simple harmonic motion can serve as a <a href="/facts/Mathematical_model/CGhyuxgz">mathematical model</a> for a variety of motions, but is typified by the oscillation of a <a href="/facts/Mass/HHdc8XmF">mass</a> on a <a href="/facts/Spring_(device)/jknGXzTq">spring</a> when it is subject to the linear <a href="/facts/Elasticity_(physics)/wcJoIFg1">elastic</a> restoring force given by <a href="/facts/Hooke%27s_law/7hTUcKUm">Hooke's law</a>. The motion is <a href="/facts/Sinusoidal/mD1CB09M">sinusoidal</a> in time and demonstrates a single <a href="/facts/Resonance/q7VLALUz">resonant</a> frequency. Other phenomena can be modeled by simple harmonic motion, including the motion of a <a href="/facts/Pendulum/D2hQXwlI">simple pendulum</a>, although for it to be an accurate model, the <a href="/facts/Net_force/XzbmueXk">net force</a> on the object at the end of the pendulum must be proportional to the displacement (and even so, it is only a good approximation when the angle of the swing is small; see <a href="/facts/Small-angle_approximation/8PQygrBq">small-angle approximation</a>). Simple harmonic motion can also be used to model <a href="/facts/Molecular_vibration/Y0ovRukI">molecular vibration</a>. </p><p>Simple harmonic motion provides a basis for the characterization of more complicated periodic motion through the techniques of <a href="/facts/Fourier_analysis/sUA8JP6q">Fourier analysis</a>. </p>