week 1 Flashcards
What is acceleration?
The rate of change of speed or velocity.
What are coordinates?
A set of numbers used to locate a point along a line or in space.
What is force?
An influence that can deform an object or cause it to change its motion.
What is gravity?
The force exerted by the Earth on all objects on or near it.
What is a joule?
A unit of energy or work; one joule is equal to one newton-meter, also one watt-second.
What is kinetic energy?
Energy of motion; the capacity to do work by virtue of that motion; equal to one half mass times velocity (or speed) squared.
What is mass?
A measure of resistance to change in motion; equal to force divided by acceleration.
What is a newton?
A unit of force.
What is potential energy?
Stored energy; the capacity to do work by virtue of position.
What is power?
The rate of doing work; equal to work or energy divided by time.
What is pressure?
Force divided by area.
What is speed?
The rate at which distance is covered; equal to distance divided by time.
What is a stroboscope?
A light that flashes at a regular rate, making possible a photographic record of motion.
What is a watt?
A unit of power; equal to one joule per second.
What is work?
The net force on an object times the distance through which the object moves.
What does ∆ represent?
The Greek letter delta, denoting change in some quantity.
What is amplitude?
Maximum displacement from rest.
What is damping?
Loss of energy of a vibrator, usually through friction.
What is an envelope?
Time variation of the amplitude (or energy) of a vibration.
What is frequency?
The number of vibrations per second; expressed in hertz (Hz).
What is the fundamental mode?
The mode of lowest frequency.
What are harmonics?
Modes of vibration whose frequencies are whole-number multiples of the frequency of the fundamental mode.
What is a Helmholtz resonator?
A vibrator consisting of a volume of enclosed air with an open neck or port.
What is longitudinal vibration?
Vibration in which the principal motion is in the direction of the longest dimension.
What is a node or nodal line?
A point or line where minimal motion takes place.
What are normal modes?
Independent ways in which a system can vibrate.
What is the period?
The time duration of one vibration; the minimum time necessary for the motion to repeat.
What is simple harmonic motion?
Smooth, regular vibrational motion at a single frequency such as that of a mass supported by a string.
What is a spectrum?
A ‘recipe’ that gives the frequency and amplitude of each component of a complex vibration.
What is the spring constant?
The strength of a spring; restoring force divided by displacement.
What is transverse vibration?
Vibration in which the principal motion is at right angles to the longest dimension.
What is a waveform?
Graph of some variable (e.g., position of an oscillating mass or sound pressure) versus time.
What is absolute temperature?
The temperature (in kelvins) on a scale that has its zero at the lowest attainable temperature (−273°C); absolute temperature is found by adding 273 to the Celsius temperature.
What is an anechoic room?
Echo free; an anechoic room is one whose walls, ceiling, and floor are covered with sound-absorbing material, usually in the shape of wedges.
What is diffraction?
The spreading out of waves when they encounter a barrier or pass through a narrow opening.
What is the Doppler effect?
The shift in apparent frequency when the source or observer is in motion.
What is an impulsive wave?
A brief disturbance or pressure change that travels as a wave.
What is interference?
The interaction of two or more identical waves, which may support (constructive interference) or cancel (destructive interference) each other.
What is a longitudinal wave?
A wave in which the vibrations are in the direction of propagation of the wave; example: sound waves in air.
What is reflection?
An abrupt change in the direction of wave propagation at a change of medium (by waves that remain in the first medium).
What is refraction?
A bending of waves when the speed of propagation changes, either abruptly (at a change of medium) or gradually (e.g., sound waves in a wind of varying speed).
What is a transverse wave?
A wave in which the vibrations are at right angles to the direction of propagation of the wave; example: waves on a rope.
What is a standing wave?
A wavelike pattern that results from the interference of two or more waves; a standing wave has regions of minimum and maximum amplitude called nodes and antinodes.
What is superposition?
The motion at one point in a medium is the sum of the individual motions that would occur if each wave were present by itself without the others.
What is wavelength?
The distance between corresponding points on two successive waves.
What is Young’s modulus?
An elastic modulus of a solid; the ratio of force per unit area to the stretch it produces.
What is acoustic impedance?
A measure of the difficulty of generating flow (in a tube, for example); it is the ratio of the sound pressure to the volume velocity due to a sound wave.
What is damping?
Energy loss in a system that slows it down or leads to a decrease in amplitude.
What is electromagnetic force?
The force that results from the interaction of an alternating electric current with a magnetic field.
What is fundamental?
The mode of vibration (or component of sound) with the lowest frequency.
What is a harmonic?
A mode of vibration (or a component of a sound) whose frequency is a whole-number multiple of the fundamental frequency.
What is linewidth?
The width of a resonance curve, usually measured at 71% of its maximum height; a measure of the sharpness of a resonance (a sharp resonance is characterized by a small linewidth).
What is an overtone?
A component of a sound with a frequency greater than the fundamental frequency.
What is a partial?
A component of a sound; includes the fundamental plus the overtones.
What is phase difference?
A measure of the relative positions of two vibrating objects at a given time; also the relative positions, in a vibration cycle, of a vibrating object and a driving force.
What is Q?
A parameter that denotes the sharpness of a resonance; Q = f0 / f, where f0 is the resonance frequency and f is the linewidth.
What is resonance?
When a vibrator is driven by a force that oscillates at a frequency at or near the natural frequency of the vibrator, a relatively large amplitude results.
What is a soundboard?
A sheet of wood or other material that radiates a substantial amount of sound when it is driven in sympathetic vibration by a vibrating string or in some other manner.
What is sympathetic vibration?
One vibrator causing another to vibrate at the same frequency (which may or may not be a resonance frequency). An example is a piano string causing the bridge and soundboard to vibrate at the string’s frequency.
