Simple Harmonic Motion Calculator NZ
This calculator works out the motion of an object undergoing simple harmonic motion, finding its position, velocity and acceleration at any instant, along with the period of oscillation. Simple harmonic motion, or SHM, is the smooth back-and-forth oscillation that appears throughout physics whenever a restoring force pulls an object back toward a central position in proportion to how far it has strayed. A mass bouncing on a spring, a pendulum swinging through small angles, a vibrating guitar string, and the oscillation of atoms and circuits all follow it. The motion is described by a few key quantities: the amplitude, the maximum displacement from the centre; the frequency, how many oscillations occur per second; and from these the angular frequency and the period. At any moment the object's position traces a cosine curve, its velocity is greatest at the centre and zero at the extremes, and its acceleration is greatest at the extremes and zero at the centre, always pointing back toward the middle. This tool computes them. You enter the amplitude, the frequency, and a time of interest, and the calculator returns the position at that time, the velocity at that time, the maximum velocity, and the period. The results update as you type, so you can trace how the motion evolves. Use it for physics problems on springs, pendulums and waves, for understanding oscillations, or for engineering vibration work. The relationships are clean: the angular frequency is two pi times the frequency, the maximum velocity is the amplitude times the angular frequency, and the maximum acceleration is the amplitude times the angular frequency squared. A defining feature of simple harmonic motion is that the period depends only on the system's properties, not on the amplitude, which is why a pendulum keeps good time whether it swings a little or a lot.
x = A cos(2 pi f t), with velocity and acceleration following. Max velocity = A x angular frequency. The period depends only on frequency, not amplitude. Rounded for display.
How it works
The angular frequency is two pi times the frequency. The position at time t is the amplitude times the cosine of the angular frequency times t, taking the object to start at maximum displacement. The velocity is minus the amplitude times the angular frequency times the sine of that angle. The maximum velocity is the amplitude times the angular frequency, and the period is one over the frequency.
Worked example
For an amplitude of 0.1 metres at a frequency of 2 hertz, the angular frequency is 4 pi, about 12.57 radians per second. At 0.1 seconds, the position is 0.1 times the cosine of 1.257 radians, about 0.0309 metres, and the velocity is about minus 1.195 metres per second. The maximum velocity is 0.1 times 12.57, about 1.257 metres per second, and the period is 0.5 seconds.
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