Simple pendulum and the small-angle limit
The familiar pendulum period requires a small swing.
Key knowledge
An ideal point-mass pendulum of length L satisfies θ̈=−(g/L)sinθ. For |θ|≪1 in radians this becomes a harmonic oscillator with period approximately 2π√(L/g). The small-angle period is independent of bob mass, but finite-amplitude periods differ from that approximation.
Values and equations
θ̈=−(g/L)sinθ; T_small≈2π√(L/g)
- θ
- Pendulum angle from downward equilibrium rad
- g
- Gravitational acceleration magnitude m s⁻²
- L
- Pivot-to-bob distance m
- T_small
- Small-angle period s
Conditions and scope
- Fixed pivot in the local inertial approximation, massless inextensible connector, L>0, uniform gravity g>0 and negligible drag/pivot friction.
- Small-angle accuracy is set by the required error tolerance; the approximation is not an exact amplitude-independent period for arbitrary swings.
Sources · 1
References
Sources retain their recorded scope. A source link alone does not establish verification of every statement.
Evidence and review
Read §15.4 simple-pendulum equation15.16 and small-angle approximation15.17–15.19. Exclude the prose’s unqualified “completely independent” amplitude statement outside the small-angle limit.
2026-10-10 · /root/audit_life_earth_chemistry — independent Chemistry/Life/Earth editor. Independent AI editorial review of this entry's statements, equations, applicability conditions and source coverage. Source checks apply to these claims within their stated limits.
Entry details
Permanent link to this entry ↗- Record identity
- foundation-physics-simple-pendulum
- Revision
- foundations-refresh.1
- Structured reference record
- Foundational reference additions