The dependence of displacement on time in harmonic motion; A is the maximum displacement, ω the angular frequency, φ the initial phase.
Symbols
x
displacement
[m]
A
amplitude
[m]
ω
angular frequency
[rad/s]
t
time
[s]
φ
initial phase
[rad]
Where it comes from
It describes the position of an oscillating body at every instant. The amplitude A is the maximum displacement, ω sets the rate of oscillation, and φ sets the state at the instant t=0.
When to use it
Harmonic motion: a spring, a pendulum at small displacements.
Example
For A=0.1 m, ω=2 rad/s, φ=0, calculate the displacement after t=π/4 s.