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MCAT Physics > Physics #7 > Flashcards

Physics #7 Flashcards

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1
Q

transverse waves

A

those in which the direction of particle oscillation is perpendicular to propagation of the wave
Ex: wave in a stadium: moves around stadium but people just go up and down.
Ex: string whipped up and down attached at one point.

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2
Q

longitudinal waves

A

the particles of the wave oscillate parallel to the direction of propagation
Ex: person pushing in and pulling out a piston
Ex: slinky on a table and tapping it, kind of bumping into each other as the wave moves down.

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3
Q

propagation

A

movement and direction of energy transfer

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4
Q

maximum value of a wave is a ____

A

crest

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5
Q

wavelength

A

distance from one crest to the next (m)

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6
Q

frequency

A

number of wavelengths passing a fixed point per second (Hz) Cycles/second

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7
Q

period

A

seconds/cycle

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8
Q

equilibrium position

A

the central point around which waves oscillate

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9
Q

displacement and amplitude

A

displacement (x): describes how far a particular point on the wave is from the equilibrium position (expressed as a vector quantity)
amplitude (A): the maximum magnitude of displacement in a wave

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10
Q

what is the distance between a crest and trough called?

A

2x the amplitude

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11
Q

trough vs. crest

A

trough: bottom of the wave
crest: top of the wave

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12
Q

phase difference

A

for waves passing each other, calculating how in step or out of step they are

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13
Q

what is the phase difference for 2 waves that completely line up?

A

0 (360 degrees)

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14
Q

what is the phase difference for 2 waves that are completely out of phase?

A

180 or lambda/2

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15
Q

the principal of superposition

A

when waves interact with each other, the displacement of the resultant wave at any point is the sum of the displacements of the two interacting waves

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16
Q

constructive interference

A

when waves are perfectly in phase, the displacements always add together and the amplitude of the resultant is equal to the sum of the amplitudes of the two waves

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17
Q

destructive interference

A

when waves are perfectly out of phase, the displacements always counteract each other and the amplitude of the resultant wave is the difference between the amplitudes of the interacting waves

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18
Q

traveling wave

A

wave that moves

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19
Q

standing wave

A

the only apparent movement of the string is fluctuation of amplitude at fixed points along the length of the string. In reality the string is moving up and down (slow-mo) but looks like it is just standing there on top and bottom in real time.

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20
Q

nodes vs. antinodes

A

nodes: points in the wave that remain at rest (amplitude is 0)
antinodes: points midway between the nodes fluctuate with maximum amplitude

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21
Q

timbre

A

quality of sound

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22
Q

what frequencies are audible to healthy adults

A

20 Hz to 20,000 Hz

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23
Q

what produces the richest sounds

A

when objects vibrate at multiple natural frequencies (a fundamental pitch and multiple overtones) that are related to each other by whole number ratios.

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24
Q

the amplitude of wave increases if the ______ is nearly identical to the natural frequency

A

forced frequency

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25
Q

if the frequency of the periodic force is equal to a natural/resonant frequency of the system, then the system is said to be ______, and the amplitude of oscillation is at a maximum

A

resonating

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26
Q

damping/attenuation

A

a decrease in amplitude of a wave caused by an applied or nonconservative force.

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27
Q

what are the units for angular frequency

A

radians per second

28
Q

wave speed

A

rate at which a wave transmits the energy or matter it is carrying

29
Q

standing wave vs. traveling wave

A

traveling wave has nodes and antinodes that move with propagation
standing wave: nodes and antinodes do not move

30
Q

are sound waves longitudinal or transverse waves?

A

longitudinal

31
Q

applying a force at the natural frequency of a system will cause the system to _____

A

resonate

increases the amplitude of oscillations

32
Q

can sound travel through the following: solids, liquids, gases, vaccum?

A

everything but vacuum because it needs deformable medium.

33
Q

bulk modulus

A

a measure of a medium’s resistance to compression

34
Q

how does the bulk modulus relate to solids, liquids, and gases

A

increases from gases to solids

35
Q

what is the speed of sound in air at 20 degrees Celsiucs?

A

343 m/s

36
Q

what medium and density is the speed of sound the fastest in?

A

solid with very low density

37
Q

pitch

A

our perception of the frequency of sound

38
Q

infrasonic vs. ultrasonic waves

A

infrasonic: less than 20 Hz
ultrasonic: more than 20,000 Hz

39
Q

doppler effect

A

describes the difference between the actual frequency of a sound and its perceived frequency when the source of the sound and the sound’s detector are moving relative to one another.

40
Q

echolocation and doppler

A

the sound bounces off of a surface and is reflected back to the animal. How long it takes to return and the change in frequency of the sound can be used to determine the position of objects in the environment and the speed at which they are moving.

41
Q

in the doppler effect equation, if the detector or the source is not moving, then _______

A

the numerator or denominator is just the speed of the sound in the medium.

42
Q

shock wave

A

speed of object is greater than speed of sound. Pressure difference created that can be detrimental to the other objects that it passes through

43
Q

what are other words for loudness or volume of sound?

A

intensity

44
Q

intensity

A

average rate of energy transfer per area across a surface that is perpendicular to the wave
power/area (w/m^2)

45
Q

what is the surface area of a sphere

A

4(pi)r^2

useful for knowing distance traveled and area covered for a sound wave

46
Q

what is the minimum intensity of hearing and the threshold of pain?

A

min: 1x10^-12 W/m^2
pain: 10 W/m^2

47
Q

attenuation affects _____, ____ and ____, but not ______

A

amplitude, intensity, sound level

not frequency

48
Q

how can sound volume vary due to interference effects?

A

beat frequency when two pitches are produced next to each other.

49
Q

the points in a standing wave with no fluctuation in displacement are called ____

A

nodes

50
Q

the points in standing waves with maximum fluctuation are called _____

A

antinodes

51
Q

closed vs. open boundaries

A

closed: nodes
open: maximal oscillation

52
Q

fundamental frequency of strings attached at both ends or open pipes

A

the first harmonic

the lowest frequency (longest wavelength) of a standing wave that can be supported by a given length of string

53
Q

first overtone of strings attached at both ends or open pipes

A

n=2

54
Q

n= 3 is known as the _____ for strings attached at both ends or open pipes

A

second overtone or third harmonic

55
Q

for strings attached at both ends, the number of antinodes present will tell you the _____

A

harmonic

or number of half wavelengths = harmonic

56
Q

for open pipes, the number of nodes will tell you ______

A

the harmonic

57
Q

the harmonic in a closed pipe is equal to the number of ______

A

quarter wavelengths supported by the pipe

58
Q

closed pipe

A

open at one end and closed on the other

59
Q

ultrasound

A

uses high frequency sound waves outside the range of human hearing to compare the relative densities of tissue in the body

uses speed pf the wave and travel time to generate a graphical representation of borders and edges within the body by calculating the traversed distance.

60
Q

doppler ultrasound

A

used to determine the flow of blood within the body by detecting the frequency shift that is associated with movement toward or away from the receiver

61
Q

how is sound produced?

A

mechanical vibrations

62
Q

to which properties of sound do amplitude and frequency correspond?

A

intensity (sound level) and pitch

63
Q

if object and source are moving in same direction at same speed what is the perceived frequency compared to the actual frequency?

A

equal

64
Q

____ is the increase in amplitude that occurs when a periodic force is applied at the natural (resonant) frequency of an object

A

resonance

65
Q

shock waves are largest when ____

A

the objet is traveling at exactly the speed of sound

MCAT Physics (12 decks)

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