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MCAT phys > waves and sound > Flashcards

waves and sound Flashcards

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MCAT flashcards
1
Q

periodic motion

A

movement of waves where they displace from 0 in a cyclic fashion

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2
Q

amplitude

A

displacement from 0 to highest point

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3
Q

period of motion

A

time T it takes to get to adjacent peaks

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4
Q

frequency

A

1/T, amont of peaks in a given amount of time
unit: hertz

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5
Q

phase difference

A

two objects in same period motion that have the same frequency but are out of sync
- visualized by the time difference between x intercepts on graphs of their motion

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6
Q

at peak of peridoic movment what is the velocity

A

0, and PE is at its highest

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7
Q

potential energy for a pendulum

A

mgh

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8
Q

potential energy for a spring

A

1/2kx^2

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9
Q

when is the KE highest for periodic motion

A

when y=o
1/2mv^2

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10
Q

what force keeps periodic motion stable

A

restoring force that trys to pull objects back to equillibrium point

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11
Q

restoring force of spring

A

-kx

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12
Q

restoring force of pendulum

A

mg (gravity)

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13
Q

equation for calculating the period of a spring

A

T= 2π/ sqrt(m/k)

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14
Q

what does a large T mean for frequency

A

low frequency

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15
Q

eqn for period of a pendulum

A

T = 2π/sqrt(L/g)

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16
Q

T

A

period, time for a cycle of motion to repeat

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17
Q

mechanical waves

A

involve actual physical motion of particles
can be transverse or longitudinal

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18
Q

transverse waves

A

particles move perpendicular to the axis of the wave
- move through water

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19
Q

longitudinal waves

A

particles move parralel to axis of wave
- move in sam direction of wave

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20
Q

propagation speed

A

speed that a wave moves through space –> depends on medium

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21
Q

units of Frequency

A

Htz or 1/s

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22
Q

propagation speed of wave eqn

A

v= f* λ
- λ is wavelength
- f is frequency

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23
Q

speed of light eqn

A

c = λ *f
c= 3.0E8 m/s

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24
Q

what happens to the frequency and wavelength of a wave when it passes through a new medium

A

frequency REMAINS THE SAME but wavelength changes with the medium

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25
Q

what is associated with higher speed of propogation

A

higher wavelength

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26
Q

interference

A

amplitidue of waves at a given location will add together to predict their behavior

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27
Q

constructive interference

A

overlapping waves have the same amplitude with the same directionality they add together to be greater than either of the components
- ammplitdues will add linearly to 2y

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28
Q

destructive interference

A

overlapping waves have amplitudes with opposite directionality and cancel out y-y = 0 if they have the exact same amplitude

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29
Q

sound waves

A

longitudinal and compressed
and we experience sound through pressure

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30
Q

pressure eqn

A

force/ area

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31
Q

what kind of material does sound move faster throgh

A

non-compressible or stiff mediums

32
Q

bulk modulus

A

vsound = sqrt(b/p)
degree that material resists compression
- speed of sound depends on density and resistance to compressibility

  • presssure needed to compress a substance
  • high b value = high resistance to compressibility
33
Q

what phase of matter has the highest bulk modulus

A

solids

34
Q

which phase of matter does sound move through the fastest

A

solids, then liquids, then gases

35
Q

intensity of sound

A

power delivered over a given area
W/m^2

36
Q

loudness

A

how intensity is percieved by ear. not same thing as intensity

37
Q

intensity is preporitional to what

A

the amplitude squared

38
Q

units of intensity

A

W/m^2 or Db

39
Q

decible scale

A

logarithmic , 12 orders of magnitude from
1.0E-12 W/m^2 to 1 W/m^2

40
Q

intensity ratio of sound in decibles

A

dB= 10log (I/Io)
I is intensity of light
Io is (1.0E-12)
ratio is from 120-130 dB

41
Q

attenuation of sound

A

decreases as distance increases

42
Q

what quality is attributed to amplitdue of a sound wave

A

loudness

43
Q

what quality is attributed to frequency of soundwave

A

pitch of sound
- increased frequency= higher pitch

44
Q

human range of pitch

A

20 hZ to 20 kHz

45
Q

doppler effect

A

an increase (or decrease) in the frequency of sound, light, or other waves as the source and observer move toward (or away from) each other. The effect causes the sudden change in pitch noticeable in a passing siren, as well as the redshift seen by astronomers.

46
Q

according to doppler, the closer the source of sound

A

the higher frequency

47
Q

doppler equation

A

F0 = Fs ( v + vo)/(v+vs)
- fo is observer frequency of sound
- Fs is frequency of source
v is speed of sound
vo is speed of observer
vs is speed of source

48
Q

when is the velocity of the observer positive

A

when observer is moving toward the source

49
Q

when is v source considered positive

A

when source is moving away from observer

50
Q

doppler eqn: when the numerator is greater than the denominator what happens?

A

frequency increases for observer

51
Q

doppler eqn: when the demoninator is greater than the numerator what happens

A

frequency decreases for observer

52
Q

ultrasound imaging

A

use high sound frequencies to image structures of body

53
Q

doppler ultrasoundography

A

frequency shifts are utilized to determine whether blood is flowing to or away from the transducer
- calculate velocity of blood moving through a vessel

54
Q

standing wave

A

stable patterns of interference among waves propagating in opposite directions
- wavelike product of multiple waves

55
Q

shape of standing wave graph

A

sigmoidal, areas with no displacement are like y=0

56
Q

points of a standing wave with 0 displacement

A

nodes

57
Q

points of a standing wave with maximum displacement

A

antinodes

58
Q

common mediums that support standing waves

A
  1. PIPE
  2. TAUT STRINGS
59
Q

taut strings

A

held tight and cannot vibrate, so the ends of the strings are nodes , and increaseing the amount of antinodes in between will increase the frequency

60
Q

first harmonic of a taut string

A

lowest possible frequency with only 1 node at one end

61
Q

second harmonic of a taut string

A

2 antinodes

62
Q

third harmonic of a taut string

A

3 antinodes

63
Q

wavelength formula of the nth harmonic of string

A

λ = 2/n (L)

64
Q

frequency formula for the nth harmoic of string

A

f= n/2 (v/L)

65
Q

pipes

A

closed ends: nodes
open ends: antinodes

66
Q

wavelength formula for the nth harmonic of a pipe with 2 open ends

A

λ= 2L/n

67
Q

difference between pipes and strings for nth harmonics

A

nth for strings refers to how many antinodes the string has
nth for open pipes refers to how many nodes the pipe has

68
Q

pipe with one closed end and one open end

A

closed end is a node
open end is an antinode

69
Q

wavelength formula for the nth harmonic with a closed end

A

λ = 4L/ n (odd)
- only works for odd number of nodes

70
Q

wavelength formula for the nth harmonic with a closed end

A

λ = 4L/ n (odd)
- only works for odd number of nodes

71
Q

frequency formula for the nth harmonic with a closed end

A

f = n(odd)/4 *v/L

72
Q

wavelength fromula for nth harmonic with open ends

A

λ= 2n/L

73
Q

frequency formula for the nth harmonic with open ends

A

f= n/2*V/L
- antinodes on open ends

74
Q

what are the ends of a 2 open pipe

A

antinodes

75
Q

what are the ends of a pipe that is closed

A

closed end is node, open is antinode

MCAT phys (9 decks)

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