SAT Subject Test Physics Flashcards
Galileo’s main principles
- Bodies dropped from the same height will all fall with the same acceleration - Principle of inertia: the natural state of motion is uniform constant velocity
Newton’s laws
1st: law of inertia, 2nd: F=ma, 3rd: when two objects interact, an equal and opposite force acts on each object
Newton’s law of gravity
Fg=G*m1*m2/r^2
James Watt
developed the concept of power
Johann Kepler’s laws of planetary motion
1st: planetary motion is elliptical, 2nd: a line drawn from the central body (Sun) to an orbiting body (planet) will sweep equal areas of space in equal time intervals, 3rd: square of the period (time of one orbit) is proportional to the radius of the orbit, T^2 = r^3
Charles Augustin De Coloumb
Fe=k*q1*q2/r^2
George Simon Ohm
Ohm’s Law: V=IR
Micahel Faraday
introduced electromagnetic fields and electromagnetic induction
Henrich Lenz
dictates the direction of an induced current in a closed loop of conducting material, based on conservation of energy
James Clerk Maxwell
mathematically demonstrated that light is an electromagnetic wave
Thomas Young
performed the famous double-slit experiment
Christian Doppler
developed the Doppler effect concept
Lord Kelvin
developed the concept of absolute zero and its associated temperature scale
James Joule
Showed that heat and work are both methods of adding energy to a system
Albert Michelson
designed a device known as an interferometer to detect the motion of Earth through the invisible ether, but this experiment failed to prove the existence of the ether
JJ Thomson
discovered the electron, and developed plum-pudding model
Max Planck
founder of quantum theory
Einstein’s miracle year
1905; published four papers that changed physics
Einstein’s major achievements
Photoelectric effect (E=hf), Special relativity, mass-energy equivalence
Ernest Rutherford
using gold foil experiment, deduced that an atom was mostly empty space with a dense positive nucleus surrounded by orbiting electrons
Neils Bohr
created “planetary model” of the atom with specific energy levels
astrophysics
the physics of celestial objects that seeks to resolve the origin of the universe and to explain its properties
chaos theory
when a complex series of events are set in motion, the results can vary drastically depending on small initial changes in the system; “the butterfly effect”
dark matter
accounts for missing mass of the universe
microprocessor
a complex, single circuit consisting of many miniaturized components. Microprocessors are based on semiconductor and transistor technology
semiconductor
a material that can act as a conductor or as an insulator (silicon most popular)
superconductor
a material that has zero electrical resistance when cooled below a critical temperature
string theory
hypothesizes that the elementary particles making up matter are actually linear oscillations or strings. This theory attempts to explain how everything interconnects, and hopes to eliminate inconsistencies among earlier theories.
transistor
can both amplify the electrical signal it receives and act as a switch. Typically has a base, collector, and emitter. A small amount of current passing through the base can control a larger current at the collector, which determines the amount of current leaving the transistor at the emitter.
essential kinematics equations
- vf2=vi2+2ax
- x=vit+(1/2)at2
Hooke’s law
Fs=kx
static equilibrium
the object has a constant velocity equal to zero
dynamic equilibrium
the object has a constant velocity not equal to zero
vertical uniform circular motion
m*v2/r = mg (no tension)
centripetal/radial acceleration
ac=v2/r
elastic potential energy
Us=(1/2)kx2
work
W = Favg Δdparallel
Work done in uniform circular motion
No work is done, because motion is perpendicular to the force
power
P = Fv = W/t
conservative forces
when conservative forces act, the total mechanical energy in a system remains constant (for example, gravity or spring forces)
example of nonconservative force
friction
linear momentum
p=mv
impulse
J=FΔt
when objects interact in a closed system, the total _____ of the objects is conserved
momentum
elastic collision
objects collide and bounce off of each other without sticking
inelastic collision
two objects that collide and stick together
conservation means that the ____ energy is conserved, not that _____ is conserved
total; a particular
in what type of collision is kinetic energy conserved?
perfectly elastic
equation for escape velocity
vorbit =sqrt(GM/r)
perihelion
when planet is closer to the Sun, it will move at faster orbital speed
aphelion
when the planet is at its farthest point from the sun and moves more slowly
charging objects by conduction vs. induction
conduction: physical touching
induction: done without physically touching the object
electric force
FE=qE
electric field of point charge
E=k(q/r2)
the direction of increasing voltage is opposite ____
the direction of the electric field lines
in parallel plate problems, the _____ is usually the high potential plate, while the ____ is usually the low potential plate
positive plate; negative plate
magnitude of electric potential at a location in a uniform electric field
V=Ed
potential difference equation
ΔV=EΔd
equipotential lines
always perpendicular to the electric field lines
electric potential of a point charge
V=k(q/r)
electric potential energy
UE = qV = k(q1)(q2)/r
work down by electric field
WE=-qΔV
capacitance of parallel plates
C=(ε0)A/d
as long as a capacitor is connected to a battery, it _____
will charge to the same voltage as that battery
capacitance in relation to charge and potential
Q=CV
energy of capacitor
UC=(1/2)(QV)=(1/2)CV2
all resistors in a series circuit receive the same ____
current
all resistors in a parallel circuit receive the same ____
voltage
equivalent resistance in parallel
1/Rp=1/R1 + 1/R2 + …
Joule’s Law of heat
Q=I2RT
Power formula in circuit
P=IV=I2R
The brightness of a lightbulb has directly to do with _____
power
domains
groups of atoms having similar magnetic orientation
How do you find the direction of magnetic field for a current-carrying wire?
Use the right-hand rule
Magnitude of magnetic field of a wire
B=(u0/2π)*(I/r), where r is distance and I is current
force from magnetic field on moving charge
Fb=qvBsinθ=q(vxB)
use the left hand for ___
negative charges
force on current-carrying wires
FB=ILxB=ILBsinθ
emf
ℰ = Δϕ/t
flux
change in area through which magnetic field passes or change in magnetic field strength
for rectangular loop entering magnetic filed, emf equals _____
BL*v
Lenz’s law
the induced current is a restoring force
period of a spring in SHM
Ts=2π*sqrt(m/k)
period of pendulum in SHM
Tp=2π*sqrt(L/g)
when a wave changes medium ___ changes, but ____ stays the same
wave speed & wavelength; frequency
electromagnetic waves from lowest to highest energy
radio waves, microwaves, visible light, ultraviolet, X-rays, gamma rays
Doppler effect
if the sound source is moving toward the observer, the observer hears a higher frequency. If it is moving away, the observer hears a lower frequency.
node & antinode of standing wave
node is where the superposition of two saves creates destructive interference, and antinodes are the locations of greatest constructive interference
how does one find the wavelength associated with a certain harmonic?
λn=(1/n)λ1
how does one find the frequency associated with a certain harmonic?
fn=nf1
beats
when there are two different frequencies being played, there will be constructive and destructive portions. The beat occurs when the destructive portions are at zero.
beat frequency
fbeat=|f1-f2|
convex lens, rules for objects at multiple points
- image at far distance will be located at the focal point on the opposite side of a converging convex lens.
]1. object outside of 2f: small image (M<1) and inside 2f on the far side
- object at 2f: image and object are same size, and at 2f on the far side.
- object between 2f and f: large image (M>1) and outside 2f on the far side.
- as objects move toward f, the image distance and image size increase.
- inside f, as object moves towards lens, image decreases in size and moves toward the lens
when the object is outside the focus of a convergent convex lens, ______. when it’s not, _____.
the image is inverted and real; the image is upright and virtual
a divergent concave lens always forms a ____
small, upright, and virtual image
for a divergent lens, when the object moves towards the lens, the image _______
also moves toward the lens and becomes larger
main difference between divergent lens and divergent mirror
the sides on which the images appear are switched
index of refraction
n=c/v (c is speed of light, v is speed of light in medium)
Snell’s law
n1sinθ1=n<span>2</span>sinθ<span>2</span>
What happens when the density of the medium of the wave changes?
more n, more dense, θ1>θ<span>2</span> (less angle)
less n, less dense, θ<span>2</span>>θ<span>1</span> (more angle)
total internal reflection
when moving to a lower density (higher angle), the new angle might hit 90 degrees. In this case, there’s simply total internal reflection. The minimum angle needed to cause total internal reflection is the critical angle.
shadow region in diffraction
when the slit is very large, there will be large shadow regions in which light is absent
Hyugens’ principle
- every oscillator in a wave creates spherical wavelets that propagate outward
- the wave front created by these oscillators is due to the combined interference of the wavelets
results of double slit experiment
bright (constructive interference) and dark (destructive intereference) spots
two mathematical relationships for young’s double-slit experiment
xm=(mλL)/d, where m is the # of the maximum, L is the space between screen and slits, and d is the space between the slits
d=mλsinθ
the path difference is equal to _____
the number of the maximum times the wavelength
polarization of light
the polarizing filter will only allow one direction of light through (the direction is perpendicular to the direction of the organic molecules in the filter)
dispersion (prism)
when white light strikes a prism, each wavelength of light ahs a different wavelength and index of refraction, so each color bends at a slightly different angle as it enters and leaves the prism, with short wavelengths having the highest index of refraction and bending the most
diffuse reflection
when light strikes a surface that is not smootha nd polished
linear expansion
ΔL = αL0ΔT
average speed of ideal gas molecules
v=sqrt(3RT/M)
average kinetic energy of gas
Kav=(3/2)kbT
pressure
P=F/A
ideal gas law
PV=NRT
heat
Q, change in thermal energy
conduction
heat is transferred when two objects at different temperatures physically touch each other
convection
heat transfer by fluids (liquids and gases)
radiation
heat transfer due to the absorption of light energy
rate of heat transfer
Q/Δt = (kAΔT)/L
(L is the length of the object, A is cross sectional area, k is thermal conductivity)
heat needed to change temperature of a substance with mass m
Q=mcΔT
to solve for heat needed in phase changes involving a substance with mass m
Q=mL, where L is the heat of transformation (L is different depending on vaporization or melting)
when heat is added to a substance that has started to melt,
temperature does not change - the heat goes towards fully melting/vaporizing the substance
thermal energy of a gas
ΔU=(3/2)nRΔT
isothermal process
temperature remains constant, so ΔU = 0
isometric/isochoric process
volume of gas remains constant, so ΔV=0, and no work is done
adiabatic process
no heat is added or removed, so Q=0
first law of thermodynamics (conservation of energy)
ΔU=Q+W
heat engine
device that converts thermal energy into other forms of energy
efficiency of heat engine
e=|QH-QC|/QH,
e=|TH-tC|/TH (note: REQUIRES KELVIN)
second law of thermodynamics
entropy of an isolated cannot decrease (always increases), and once at equilibrium, entropy remains constant
heat pump
transfers heat opposite the natural direction of movement, but must use energy greater than the energy released if the heat flowed normally
Albert Einstein’s photoelectric effect equations
E=hf (energy is proportional to frequency), E=hc/λ
increasing the frequency of photons for photocell does what?
increase potential of photocell and energy of emitted electrons
equation of energy of emitted electrons in photocell
Kmax=hf-ϕ
what happens when light intensity is increased in photocell?
increases number of electrons emitted and the current
alpha particle
helium with 2 neutrons, 2 protons
beta particle
no mass number, but has a -1 charge (basically an electron)
gamma ray
has no mass, just a radiation
most massive fundamental particles to least massive
alpha particle, neutron, proton, electron/beta particle, neutrino, gamma radiation
mass-energy equivalence
E=(Δm)c2
if you see a moving light source, _____
light will always appear at the same speed
an object moving near or similar to the speed of light…
time will DILATE (clock on object appears to be going slowly), length CONTRACT (length affected only in direction of motion), mass will INCREASE (mass of a moving object will appear larger)
convergent
convex lens, concave mirror
divergent
concave lens, convex mirror
equations for lenses and mirrors
f=R/2 (R=radius of curvature0
1/f = 1/d0 + 1/di
M = hi/h0 = -di/d0
convergent properties (convex lens and concave mirror)
If the object is outside f, the image is inverted (-hi) and real (+si). If the object is at f, the image is at infinity. If the object is inside f, the image is upright (+hi) and virtual (-si)
