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Shenyi > physics def > Flashcards

physics def Flashcards

1
Q

Newton’s First Law of Motion

A

An object will remain in a constant velocity (or at rest) unless a resultant external force acts upon it.

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2
Q

Centripetal acceleration

A

The acceleration due to a changing velocity direction. It points toward the centre of the circular path and equals (v^2)/r.

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3
Q

displacement

A

distance in a specified direction

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4
Q

acceleration

A

rate of change of velocity

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5
Q

instantaneous velocity

A

velocity at a moment in time

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6
Q

linear momentum

A

product of mass and velocity

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7
Q

impulse

A

force × time
change in momentum

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8
Q

Newton’s second law

A

the acceleration of a body is proportional to the force applied and inversely proportional to its mass

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9
Q

Newton’s third law

A

when two bodies A and B interact the force that A exerts on B is equal and opposite to the force that B exerts on A

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10
Q

conservation of linear momentum

A

the momentum of a system is constant for an isolated system

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11
Q

work

A

force applied in direction of movement x displacement

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12
Q

conservation of energy

A

energy cannot be created or destroyed, it just changes form

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13
Q

elastic collision

A

collision in which momentum and kinetic energy are both conserved

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14
Q

inelastic collision

A

collision in which only momentum is conserved, kE is lost(transferred)

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15
Q

power

A

rate of doing work

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16
Q

efficiency

A

ratio of useful output work to total input work

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17
Q

thermal equilibrium

A

system of bodies at the same temperature

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18
Q

internal energy

A

total potential energy and random kinetic energy of the molecules of the substance

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19
Q

thermal energy

A

non-mechanical transfer of energy between a system and its surroundings

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20
Q

mole

A

amount of a substance containing same number of particles as atoms in 0.012kg of carbon-12

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21
Q

Avogadro constant

A

the number of particles in one mole

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22
Q

specific heat capacity

A

quantity of thermal energy required to raise temperature of unit mass by 1K

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23
Q

thermal capacity

A

the energy required to raise the temperature of a substance by 1K

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24
Q

evaporation
and boiling

A

takes place at the surface of a liquid and at any temperature
takes place thoughout the liquid and always at the same temperature

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25
Q

specific latent heat

A

the amount of energy associated with phase change

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26
Q

specific latent heat of fusion or vaporization which is bigger

A

solid to liquid
liquid to gas
vaporization is larger as more bonds to break

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27
Q

pressure

A

force per unit area

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28
Q

assumptions of kinetic model

A

all particles are considered as points

perfectly elastic (no energy lost) collisions with

no forces and potential energy between particles except during collisions.

molecules are in random motion.

the volume of the particles is very small compared to the gas volume.

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29
Q

ideal gas

A

gas made from particles obeying the assumptions of the kinetic model

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30
Q

temperature and KE

A

temperature is a measure of the random KE of molecules of an ideal gas

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31
Q

boyles’s law

A

at constant temp, the pressure and volume of a gas is inversely proportional.

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32
Q

amplitude

A

in any periodic motion, the maximum displacement from equilibrium

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33
Q

simple harmonic motion

A

repeated motion caused by acceleration that is directed towards the centre

a is proportional but opposite in the direction to the displacement from the EL position.

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34
Q

phase difference

A

difference, in angle or time, between two waves of the same frequency at the same time

in phase-0 degree pd
out of phase-180 degrees pd

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35
Q

wavelength

A

distance moved by wave during one oscillation of the source

distance between adjacent crests

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36
Q

diffraction effects

A

waves propagate

less if the gap is bigger

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37
Q

universal wave equation

A

v=f lamda

f determined by oscillator creating waves

change in medium affect v, affect lamda

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38
Q

damping

A

progressive reduction in amplitude of SHM caused by a dissipative force opposing direction of motion

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39
Q

natural frequency of oscillation

A

the resonant frequency - the frequency at which resonance occurs

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40
Q

resonance

A

behaviour of a system when a periodic force is applied with a frequency equal to the system’s natural frequency of oscillation, the amp becomes very large

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41
Q

transverse wave

A

wave with oscillations perpendicular to the direction of energy propogation(motion of the wave)

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42
Q

longitudinal wave

A

wave with oscillations parallel to the direction of energy propagation

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43
Q

standing waves

A

particles oscillate with different amps, overall amp is 2 times component wave amp

formed when 2 identical waves(same amp and f) pass through each other

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44
Q

closed pipes

open pipes

what r the length in closed and open pipe at f1,f3.

A

anodes(在两端） at the opening, node at closing, f(N)=nf(1), f1=lamda/2, f3=(3/2)lamda

anodes at both ends, f1=lamda/4
f(N)=(2n-1)f(1), f3=(5/4)lamda

45
Q

harmonics

A

when there are boundary conditions at both ends, only certain wavelength and frequencies can fit those conditions, these frequencies are called harmonics.

1 harmonics has lowest frequency

46
Q

travelling wave

A

a wave that transfers energy without any net movement of the medium

the only way to change the v of wave is to change medium

47
Q

compression
rarefaction

A

points on a longitudinal wave of maximum density

points on a longitudinal wave of minimum density

48
Q

ray

A

part of a wave travelling in a straight line in direction of propagation

49
Q

intensity

A

power per unit area: proportional to amplitude ^2

50
Q

Snell’s Law

refractive index 什么时候less than 1

A

sin (angel of refraction) ÷ sin (incidence) is a constant

slow to fast medium, n less than 1

51
Q

refractive index

A

ratio of the speeds of a wave in two media

air:1,别的都比他大

52
Q

principle superposition

A

if two or more waves overlap the resultant displacement at any point is found by adding the displacements of each individual wave

53
Q

constructive interference

destructive

A

waves reinforcing each other by superposition

waves cancelling each other by superposition

54
Q

polarizer

analyzer

A

polarizes the incoming light ，the electric field oscillates in a single plane

Completely block off the light(equation 里的angle是他的）

55
Q

critical raye&angle

total internal reflection

A

the ray that has a refracted angle of 90 degrees

angle of incidence for the critical ray, ray with angle greater than this can not be refracted

56
Q

polarized light

A

light whose waves have their E-fields oriented in one direction.
Polarization only applies to transverse waves.

polarization prevents waves vibrating in certain directions.

57
Q

reflection
refraction

A

occurs when a wave meets a boundary,
at least partially diverted backwards.

and at least partially allowed through the boundary.

58
Q

electric potential difference

A

energy per unit charge to move positive test charge between points

59
Q

electronvolt

A

the amount of kinetic energy gained by a single electron when accelerated through an electric potential difference of one volt

60
Q

electric current

A

a flow of charge

61
Q

Ohm’s law

A

current is proportional to potential difference if temperature of material is constant

constant resistance

62
Q

electromotive force

A

power supplied per unit current

63
Q

internal resistance

A

resistance of components within itself leading to power loss in a cell

64
Q

series circuit

Parallel circuit

A

current is the same

voltage is the same

65
Q

right hand role for wire&particle

A
66
Q

ideal voltmeter

ideal ammeter

A

connected in parallel, maximum resistance

minimum resistance

67
Q

Newton’s universal law of gravitation

A

force between two small masses is equal to the product of their masses and inversely proportional to the separation squared

68
Q

gravitational field strength

A

the force exerted per unit mass on a small mass

69
Q

gravitational potential

equipotential surfaces

A

the gpe per unit mass in bring a massive object to that point from some defined position of zero potential, usually infinity .

work done in moving pts along equipotential surfaces is zero.

70
Q

Coulomb’s law

A

force between two point charges is equal to the product of their charges and inversely proportional to the separation squared

71
Q

electrical field strength

A

force per unit charge felt by a positive test charge placed in an electric field

72
Q

magnitude of a magnetic field

A

the magnetic flux density, B

73
Q

direction of a magnetic field

A

north to south

74
Q

nuclide
nucleon

A

an atomic nucleus

particle found in the nucleus of an atom (proton or neutron)

75
Q

isotope

A

set of nuclei for a single element having different numbers of neutrons

76
Q

alpha particle

A

product of nuclear decay, identical to a helium nucleus
2 protons , two neutrons

77
Q

beta particle

A

product of nuclear decay, identical to an electron

78
Q

gamma ray

A

by-product of nuclear decay, a form of EM radiation
a photon

79
Q

half-life

A

the time taken for activity / mass / number of original nuclei to halve

80
Q

mass defect

A

the amount by which the mass of a particular nucleus is less than the total mass of its constituent particles

81
Q

binding energy

A

the energy released when nuclides form from constituents

energy required to separate nucleus into separate nucleons

82
Q

fission and fusion

A

large nuclei are induced to break up into smaller nuclei and release E in the process, splitting of nuclei

small.. to join tg into large nuclei and release E in the process, fusing of nuclei

83
Q

quarks

leptons

force carriers

A

heavier particles, Make up particles like protons and neutrons.

lighter, make up electrons

particles that allow compatible to react with each others through exchange of those carriers.

84
Q

hadron

baryon

meson

conservation of baryon number in all rxns

A

particles that participates in the strong force

made of three quarks

made of a quark and an antiquark, as low as we can go.

85
Q

quark confinement

A

we cannot ever separate a single quark to form a baryon or a meson.

meson和磁铁一样会质疑split

86
Q

the feyman diagrams

A

x-axis time

y-axis space

87
Q

b- decay

b+ decay

energy of beta

A

neutron to proton and (electron and antineutrino)

proton to neutron and (positron and neutrino)

could have a variety of energy

88
Q

specific energy

energy density

A

how much energy you can get per kg of fuel

how much energy you can get per unit volume

89
Q

albedo

A

power scattered /power incident

mirror near 1

black body=0

snow, ice, desert all high

90
Q

surface heat capacity

A

the energy required to raise the temp. of a unit area of a planet’s surface by one degree

91
Q

coefficient of volume expansion

A

the fractional change in volume of a material per degree change in temp.

92
Q

2nd law of thermodynamics

A

impossible to convert all heart into mechanical energy cuz of heat loss

93
Q

secondary energy source

A

energy source which has been transformed from a primary energy source before used by consumers.

94
Q

black body

A

emits as much power as it absorbs

95
Q

solar constant

average incident solar radiation

A

1380 W per m^-2

340 W per m^-2

96
Q

emissivity

A

quantifies the emission and absorption properties of that body as compared to a blackbody of EQUAL SIZE

black body=1
0: can’t emit/absorb radiation at all

97
Q

the greenhouse effect

A

gases(methane, CO2, N2O) comprising the atmosphere can absorb the infrared radiation
atmosphere traps heat, temp rise.

98
Q

Avogadro Constant

A

N(number of atoms)/n(number of mol)

98
Q

Avogadro Constant

A

N(number of atoms)/n(number of mol)

99
Q

radius of earth

A

5.67*10^8 m

100
Q

why conservation laws are significant

A

allow predictions for
possible outcomes
missing particles and quantities

model scenarios
calculate unknown variables

101
Q

why high temperatures are required for fusion

A

fusion is joining 2 or more particles tg
higher temp means higher KE which is needed to overcome the repulsion between the protons in particles and create the fused particle.

101
Q

why high temperatures are required for fusion

A

fusion is joining 2 or more particles tg
higher temp means higher KE which is needed to overcome the repulsion between the protons in particles and create the fused particle.

101
Q

why high temperatures are required for fusion

A

fusion is joining 2 or more particles tg
higher temp means higher KE which is needed to overcome the repulsion between the protons in particles and create the fused particle.

102
Q

beta minus decay
beta plus decay

A

neutron变proton electron, neutrino
proton 变 neutron positron, anti neutrino

103
Q

capicitor

A

an electronic device that stores charge.
unit:F （C over V）

104
Q

capacitance in parallel and series
parallel C=C1+C2
series 1/C=1/C1+1/C2
怎么derive

A

conservation of charge. energy

105
Q

how to increase the ability of a capacitor to store energy

A

increase the parallel area of conductive plates
decrease the distance between plates
increase the volt

Shenyi (6 decks)

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