Amplitude
The maximum displacement of an oscillating object from its equilibrium position, measured in metres. Denoted by A, amplitude represents the extent of oscillation. In SHM, amplitude is constant (in the absence of damping) and does not affect the period; instead, it determines the object's maximum speed (v_max = ωA) and maximum acceleration (a_max = ω²A).
Formula
v_max = ωA ; a_max = ω²A ; E ∝ A²
Real World
A guitarist plucking a string more forcefully increases its amplitude, making the note louder (more energy), but the pitch (frequency/period) stays the same — a direct demonstration of SHM's isochronism.
Exam Focus
Distinguish amplitude from displacement in calculations: amplitude is the maximum value of x, and must not be confused with instantaneous displacement.
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