Topic 4a: periodic motion

Page 1

Periodic motion: aka harmonic motion, any motion that repeats in regular intervals. Observed in mass on a spring, simple pendulums, molecular vibration.

Amplitude: maximium displacement from equilibrium, always positive because only magnitude is considered

cycle: one complete repetition of the motion

Period: the duration of each cycle; f/t

frequency: the number of cycles part time; f=1/t

period and frequency are inversely related

angular frequency: angular displacement per time; ω=2πf

Phase: the position of a point in time on a cycle of the waveform, the argument of the cosine function

Phase constant: the position of the particle when time equals 0

Page 2

Transverse waves: particles also late up and down, perpendicular to the direction of wave propagation. Ex: waves of light

longitudinal waves: waves in which the displacement of particles is in the direction of wave propagation. Ex: waves of sound

wavelength: the distance between repetitions of the wave, measured parallel to the travel direction of the wave

propagation speed of the wave equals (one wavelength) over (the period); (distance to repeat the cycle) over (the time to complete that cycle)

the speed of a wave along a stretched string depends only on the tension and density of the string