Definitions SHM and waves

Pregunta	Respuesta
Examples of oscillations	a pendulum, a swing, a car going over bumps
Cycle	one cycle is defined as one complete oscillation of the pendulum (A-B-A). (the term cycle is also used to describe circular motion; one cycle is one complete circle or 2pi radians)
Equilibrium position	the position where the pendulum bob would rest if not disturbed - this is position O
Amplitude (x0)	the amplitude is defined as the maximum displacement from the equilibrium position, this is distance OB or OA, (m)
Time period (T)	time taken for one complete cycle (seconds)
Frequency (f)	number of cycles that the pendulum makes per unit time. this is equal to 1/time period. (s^-1 or hertz (Hz))
Angular frequency (w(curved "w" really...))	found by multiplying f by 2pi (w=2pi f). this quantity is normally used when describing circular motion. an angular frequency of 2pi rads s^-1 means that a body makes one revolution per second. however, it is also used to describe an oscillation, 2pi being equivalent to one complete cycle. (s^-1 or Hz)
When stretching a spring, the tension is...	...proportional to the extension
Simple harmonic motion (SHM)	the acceleration is proportional to the distance froma fixed point. the acceleration is always directed towards a fixed point
When calculating cos wt, you must have your calculator set on...	...radians
Interchange between KE and PE during SHM	at the top of the swing the mass (pendulum) has maximum PE and minimum KE. at the bottom of the swing the mass has maximum KE and minimum PE
Total energy	total energy=KE+PE
Potential energy	potential energy at any moment = total energy - KE
Light damping	if the opposing forces are small, the result is a gradual loss of total energy. this means that the amplitude of the motion gets slowly less with time.
Critical damping	critical damping occurs if the resistive force is so big that the system returns to its equilibrium position without passing through it. this would be the case if a mass on a spring were suspended in for example oil
Forced oscillation	if a system is forced to oscillate at a frequency other than the natural frequency
Resonance	increase in amplitude that occurs when an oscillating system is forced to oscillate at its own natural frequency
In phase	same displacement at the same time
Out of phase	different displacement at same time
Reflection (of a (water) wave)	if a water wave hits a wall, the waves reflect
Refraction	change of direction, waves are bending
Interference	when two waves cross each other, they can add together (or cancel out) creating an extra big wave (or result in no wave!)
Diffraction	when (water) waves pass through a small opening the waves spread out
Also waves	anything that reflects, refracts, interferes and diffracts can also be called a wave
Wave pulse	(if a string held between two people is displaced (flicked),) a disturbance can be seen to travel from one end to another
Wave speed	the wave pulse travels with a certain speed, distance travelled by the wave profile per unit time (if a string held between two people is flicked and creates a wave)
Transfer of energy	as a string is lifted up, it is given PE. this PE is transferred along the string, and a wave can therefore be thought of as a transfer of energy
Wave properties	Image: wave_properties.JPG (image/JPG)
Example of transverse waves	wave in a string, light. (the direction of disturbance is perpendicular to the direction that the wave profile moves)
Example of longitudinal waves	sound, compression wave in a slinky. (the disturbance is parallel to the direction of the wave)
What type of waves can be polarized?	only transverse waves. a wave is polarized if the displacemnt is only in one direction
Constructive interference	two in phase waves add to give a wave of twice the amplitude
Destructive interference	two out of phase waves cancel
Wave poperties, two-dimensional waves	Image: Wave_properties_wavefronts (image/png)
Wavefront	this is a line joining points that are in phase, straight or circular lines
Rays	rays are lines drawn to show the direction of the waves - they are always at right angles to the wavefront
Circular wavefronts	produced by a point disturbance. the rays are radial, as they are perpendicular to the wavefronts. (for example a waterdrop landing in a pool of water - point disturbance)
Plane wavefront	produced by an extended disturbance, for example a long piece of wood dipped into the water, or a point that is so far away that the circles it produces look like straight lines
Reflection	when a wave hits a barrier, it is reflected. note that the reflected wave appears to originate from somewhere on the other side of the barrier, same as when looking at yourself in a mirror
The laws of reflection	describes how waves are reflected of barriers. ~the angle of incidence = the angle of reflection. ~the incident and reflected rays are in the same plane as the normal
Transmitted part of a wave	the part of the wave that passes through a medium; not reflected
Refraction	the change of direction when a wave passes from one medium to another
Snell's law	sin i(ncident)/sin r(efracted)=v1/v2
Refractive index	the ratio of the velocity of light in the two medias, found by using Snell's law. if the refractive index is large then the light is refracted by a large angle
Refractive index of water, glass and diamond	water - 1,33. glass - 1,50. diamond - 2,42
Diffraction	takes place when a wave passes through a small opening. if the opening is very small, then the wave behaves just like a point source
Phase angle	if the waves are completely out of phase then phase angle = pi. if not completely out of phase, the phase angle can be calculated from the path difference (d). phase angle (strange "t"-looking symbol)=2pid/lambda (wavelength)
Standing (stationary) wave	if a continuous wave is sent along a rope, the original and reflected wave superpose to produce a wave where the peaks simply move up and down but don't progress along the rope. occurs whenever two identical waves travelling at opposite directions superpose. the wave profile doesn't progress
Antinode	the opposite of a node... maximum amplitude, 2A since two waves add together
Node	the opposite of an antinode... minimum displacement, A=0
Differences between progressive waves and standing waves	~the wave profile of a standing wave doesn't progress. ~all points in between teo nodes on a standing wave are in phase whereas points in a progressive wave that are closer than one wavelength are all out of phase. ~all points on a progressive wave have the same amplitude, but on a standing wave some points have zero amplitude (nodes) and some points have large amplitude (antinodes)
Formula for calculating frequency for a standing wave (with nodes as ends)	f=v/lambda
Calculating wave speed (v) in a string	v= (square root of) T/u. T= tension, u (greek letter "miu"(??)) =mass per unit length
Sound wave	a propagation of disturbance in air pressure. the change in air pressure causes the air to move backwards and forwards in the direction of the propagation
When a standing wave is formed in a closed pipe, only _____ harmonics are formed	odd
A standing wave in an open pipe will have ___________ at both ends	antinodes
The Doppler effect	"eeeeeeeeeeeeoowwwwwww" sound, the sound on approach is a higher frequency than on retreat. can occur when the source of the sound is moving or when the observer is moving, or when both is moving

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	Creado por Moa Lindström hace más de 10 años