physics def Flashcards
(108 cards)
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.
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.
3
Q
displacement
A
distance in a specified direction
4
Q
acceleration
A
rate of change of velocity
5
Q
instantaneous velocity
A
velocity at a moment in time
6
Q
linear momentum
A
product of mass and velocity
7
Q
impulse
A
force × time
change in momentum
8
Q
Newton’s second law
A
the acceleration of a body is proportional to the force applied and inversely proportional to its mass
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
10
Q
conservation of linear momentum
A
the momentum of a system is constant for an isolated system
11
Q
work
A
force applied in direction of movement x displacement
12
Q
conservation of energy
A
energy cannot be created or destroyed, it just changes form
13
Q
elastic collision
A
collision in which momentum and kinetic energy are both conserved
14
Q
inelastic collision
A
collision in which only momentum is conserved, kE is lost(transferred)
15
Q
power
A
rate of doing work
16
Q
efficiency
A
ratio of useful output work to total input work
17
Q
thermal equilibrium
A
system of bodies at the same temperature
18
Q
internal energy
A
total potential energy and random kinetic energy of the molecules of the substance
19
Q
thermal energy
A
non-mechanical transfer of energy between a system and its surroundings
20
Q
mole
A
amount of a substance containing same number of particles as atoms in 0.012kg of carbon-12
21
Q
Avogadro constant
A
the number of particles in one mole
22
Q
specific heat capacity
A
quantity of thermal energy required to raise temperature of unit mass by 1K
23
Q
thermal capacity
A
the energy required to raise the temperature of a substance by 1K
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
25
specific latent heat
the amount of energy associated with phase change
26
specific latent heat of fusion or vaporization which is bigger
solid to liquid
liquid to gas
vaporization is larger as more bonds to break
27
pressure
force per unit area
28
assumptions of kinetic model
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.
29
ideal gas
gas made from particles obeying the assumptions of the kinetic model
30
temperature and KE
temperature is a measure of the random KE of molecules of an ideal gas
31
boyles's law
at constant temp, the pressure and volume of a gas is inversely proportional.
32
amplitude
in any periodic motion, the maximum displacement from equilibrium
33
simple harmonic motion
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.
34
phase difference
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
35
wavelength
distance moved by wave during one oscillation of the source
distance between adjacent crests
36
diffraction effects
waves propagate
less if the gap is bigger
37
universal wave equation
v=f lamda
f determined by oscillator creating waves
change in medium affect v, affect lamda
38
damping
progressive reduction in amplitude of SHM caused by a dissipative force opposing direction of motion
39
natural frequency of oscillation
the resonant frequency - the frequency at which resonance occurs
40
resonance
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
41
transverse wave
wave with oscillations perpendicular to the direction of energy propogation(motion of the wave)
42
longitudinal wave
wave with oscillations parallel to the direction of energy propagation
43
standing waves
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
44
closed pipes
open pipes
what r the length in closed and open pipe at f1,f3.
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
harmonics
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
travelling wave
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
compression
rarefaction
points on a longitudinal wave of maximum density
points on a longitudinal wave of minimum density
48
ray
part of a wave travelling in a straight line in direction of propagation
49
intensity
power per unit area: proportional to amplitude ^2
50
Snell's Law
refractive index 什么时候less than 1
sin (angel of refraction) ÷ sin (incidence) is a constant
slow to fast medium, n less than 1
51
refractive index
ratio of the speeds of a wave in two media
air:1,别的都比他大
52
principle superposition
if two or more waves overlap the resultant displacement at any point is found by adding the displacements of each individual wave
53
constructive interference
destructive
waves reinforcing each other by superposition
waves cancelling each other by superposition
54
polarizer
analyzer
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
critical raye&angle
total internal reflection
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
polarized light
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
reflection
refraction
occurs when a wave meets a boundary,
at least partially diverted backwards.
and at least partially allowed through the boundary.
58
electric potential difference
energy per unit charge to move positive test charge between points
59
electronvolt
the amount of kinetic energy gained by a single electron when accelerated through an electric potential difference of one volt
60
electric current
a flow of charge
61
Ohm's law
current is proportional to potential difference if temperature of material is constant
constant resistance
62
electromotive force
power supplied per unit current
63
internal resistance
resistance of components within itself leading to power loss in a cell
64
series circuit
Parallel circuit
current is the same
voltage is the same
65
right hand role for wire&particle
66
ideal voltmeter
ideal ammeter
connected in parallel, maximum resistance
minimum resistance
67
Newton's universal law of gravitation
force between two small masses is equal to the product of their masses and inversely proportional to the separation squared
68
gravitational field strength
the force exerted per unit mass on a small mass
69
gravitational potential
equipotential surfaces
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
Coulomb's law
force between two point charges is equal to the product of their charges and inversely proportional to the separation squared
71
electrical field strength
force per unit charge felt by a positive test charge placed in an electric field
72
magnitude of a magnetic field
the magnetic flux density, B
73
direction of a magnetic field
north to south
74
nuclide
nucleon
an atomic nucleus
particle found in the nucleus of an atom (proton or neutron)
75
isotope
set of nuclei for a single element having different numbers of neutrons
76
alpha particle
product of nuclear decay, identical to a helium nucleus
2 protons , two neutrons
77
beta particle
product of nuclear decay, identical to an electron
78
gamma ray
by-product of nuclear decay, a form of EM radiation
a photon
79
half-life
the time taken for activity / mass / number of original nuclei to halve
80
mass defect
the amount by which the mass of a particular nucleus is less than the total mass of its constituent particles
81
binding energy
the energy released when nuclides form from constituents
energy required to separate nucleus into separate nucleons
82
fission and fusion
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
quarks
leptons
force carriers
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
hadron
baryon
meson
conservation of baryon number in all rxns
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
quark confinement
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
the feyman diagrams
x-axis time
y-axis space
87
b- decay
b+ decay
energy of beta
neutron to proton and (electron and antineutrino)
proton to neutron and (positron and neutrino)
could have a variety of energy
88
specific energy
energy density
how much energy you can get per kg of fuel
how much energy you can get per unit volume
89
albedo
power scattered /power incident
mirror near 1
black body=0
snow, ice, desert all high
90
surface heat capacity
the energy required to raise the temp. of a unit area of a planet's surface by one degree
91
coefficient of volume expansion
the fractional change in volume of a material per degree change in temp.
92
2nd law of thermodynamics
impossible to convert all heart into mechanical energy cuz of heat loss
93
secondary energy source
energy source which has been transformed from a primary energy source before used by consumers.
94
black body
emits as much power as it absorbs
95
solar constant
average incident solar radiation
1380 W per m^-2
340 W per m^-2
96
emissivity
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
the greenhouse effect
gases(methane, CO2, N2O) comprising the atmosphere can absorb the infrared radiation
atmosphere traps heat, temp rise.
98
Avogadro Constant
N(number of atoms)/n(number of mol)
98
Avogadro Constant
N(number of atoms)/n(number of mol)
99
radius of earth
5.67*10^8 m
100
why conservation laws are significant
allow predictions for
possible outcomes
missing particles and quantities
model scenarios
calculate unknown variables
101
why high temperatures are required for fusion
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
why high temperatures are required for fusion
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
why high temperatures are required for fusion
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
beta minus decay
beta plus decay
neutron变proton electron, neutrino
proton 变 neutron positron, anti neutrino
103
capicitor
an electronic device that stores charge.
unit:F （C over V）
104
capacitance in parallel and series
parallel C=C1+C2
series 1/C=1/C1+1/C2
怎么derive
conservation of charge. energy
105
how to increase the ability of a capacitor to store energy
increase the parallel area of conductive plates
decrease the distance between plates
increase the volt
