Calculators/Physics/Simple harmonic motion

Simple harmonic motion

x = A·sin(ωt+φ) · displacement, velocity, acceleration

Simple harmonic motion — illustration
Displacement x(t)
0.1
m
Velocity v(t)
0
m/s
Acceleration a(t)
-0.987
m/s²
ω3.1416 rad/s
f0.5 Hz
v_max0.3142 m/s
a_max0.987 m/s²

Simple harmonic motion: x = A·sin(ωt+φ), ω = 2π/T. The velocity is maximal at the equilibrium position (x=0), and the acceleration at the extreme displacement, where a = −ω²·x.

Harmonic motion (oscillation) is described by the displacement equation:

x(t)=Asin⁡(ωt+φ),ω=2πTx(t)=A\sin(\omega t+\varphi),\qquad \omega=\frac{2\pi}{T}

where AA is the amplitude, ω\omega — the angular frequency, φ\varphi — the initial phase. Differentiating, we obtain the velocity and acceleration:

v=Aωcos⁡(ωt+φ)a=−Aω2sin⁡(ωt+φ)=−ω2xv=A\omega\cos(\omega t+\varphi)\qquad a=-A\omega^2\sin(\omega t+\varphi)=-\omega^2 x

The velocity is greatest at the equilibrium position (x=0x=0), and the acceleration — at the extreme displacement. The calculator computes x, v, a at a given instant together with the maximum values vmax=Aωv_{max}=A\omega, amax=Aω2a_{max}=A\omega^2.

Examples

A=0.1 m, T=2 s, φ=0, t=0.5 s
→ x = 0.1 m (extreme displacement), v = 0, a = −ω²x
Maximum values
→ v_max = Aω, a_max = Aω²

Frequently asked questions

Where is the velocity greatest?+

At the equilibrium position (x = 0), where the body passes fastest. At the extreme displacements the velocity is zero (the body momentarily stops).

What is the relationship between acceleration and displacement?+

a = −ω²·x — the acceleration always points toward the equilibrium position and is proportional to the displacement. This is the definition of harmonic motion.

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