Waves

Physical Pendulum Period

Period of a rigid body oscillating about a pivot point (physical/compound pendulum).

Variables

T
Period
Time for one oscillation
s
I
Moment of inertia
About pivot point
kg·m²
m
Mass
Total mass of pendulum
kg
g
Gravitational acceleration
≈ 9.8 m/s²
m/s²
d
Distance to center of mass
From pivot to CM
m

Derivation

Torque τ = -mgd·sin(θ) ≈ -mgdθ for small angles. Using τ = Iα: Iα = -mgdθ, giving ω² = mgd/I and T = 2π√(I/mgd).

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