### Key Terms

- amplitude (
*A*) - maximum displacement from the equilibrium position of an object oscillating around the equilibrium position

- critically damped
- condition in which the damping of an oscillator causes it to return as quickly as possible to its equilibrium position without oscillating back and forth about this position

- elastic potential energy
- potential energy stored as a result of deformation of an elastic object, such as the stretching of a spring

- equilibrium position
- position where the spring is neither stretched nor compressed

- force constant (
*k*) - characteristic of a spring which is defined as the ratio of the force applied to the spring to the displacement caused by the force

- frequency (
*f*) - number of events per unit of time

- natural angular frequency
- angular frequency of a system oscillating in SHM

- oscillation
- single fluctuation of a quantity, or repeated and regular fluctuations of a quantity, between two extreme values around an equilibrium or average value

- overdamped
- condition in which damping of an oscillator causes it to return to equilibrium without oscillating; oscillator moves more slowly toward equilibrium than in the critically damped system

- period (
*T*) - time taken to complete one oscillation

- periodic motion
- motion that repeats itself at regular time intervals

- phase shift
- angle, in radians, that is used in a cosine or sine function to shift the function left or right, used to match up the function with the initial conditions of data

- physical pendulum
- any extended object that swings like a pendulum

- resonance
- large amplitude oscillations in a system produced by a small amplitude driving force, which has a frequency equal to the natural frequency

- restoring force
- force acting in opposition to the force caused by a deformation

- simple harmonic motion (SHM)
- oscillatory motion in a system where the restoring force is proportional to the displacement, which acts in the direction opposite to the displacement

- simple harmonic oscillator
- a device that oscillates in SHM where the restoring force is proportional to the displacement and acts in the direction opposite to the displacement

- simple pendulum
- point mass, called a pendulum bob, attached to a near massless string

- stable equilibrium point
- point where the net force on a system is zero, but a small displacement of the mass will cause a restoring force that points toward the equilibrium point

- torsional pendulum
- any suspended object that oscillates by twisting its suspension

- underdamped
- condition in which damping of an oscillator causes the amplitude of oscillations of a damped harmonic oscillator to decrease over time, eventually approaching zero