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66 Cards in this Set

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Rules of thermal radiation
1. Hotter objects emit more total radiation per unit surface area. funkyothingT^4=E
F.O.: constant
T: temp (K)
E: light energy emitted per unit area (brightness)
2. Hotter objects emit bluer photons (w/ higher average energy)
peak wavelength=2.9x10^6/T(K) nm
Kirchhoff's Laws
1. hot, dense glowing object (solid or gas) emits <u>continuous spectrum</u>.
2. Hot, low density gas emits light of only certain wavelength: emission line spectrum.
3. When light having continuous spectrum passes thru cool gas, absorption line spectrum.
lunar eclipse
Moon passes thru Earth's shadow, can only occur at full moon
solar eclipse
occurs when moon's shadow falls on Earth and therefore can only occur at new moon
umbra
central region of shadow where sunlight is completely blocked
penumbra
surrounding region of shadow where sunlight is only partially blocked
eclipse can occur when:
Nodes are nearly aligned with Sun and Earth
the phase of Moon is new or ful
Precession is caused by
gravitational tugs from sun and moon that try to straighten out its rotational axis
total lunar eclipse
moon passes entirely through umbra
sun, earth, and moon nearly perfectly aligned
partial lunar eclipse
part of the moon passes through umbra
alignment somewhat less perfect
penumbral lunar eclipse
moon passes through penumbra
total solar eclipse
Moon is relatively close to Earth in its orbit; umbra touches a small area of Earth's surface. anyone within this area will see a total solar eclipse.
lunar eclipse
Moon passes thru Earth's shadow, can only occur at full moon
solar eclipse
occurs when moon's shadow falls on Earth and therefore can only occur at new moon
umbra
central region of shadow where sunlight is completely blocked
penumbra
surrounding region of shadow where sunlight is only partially blocked
eclipse can occur when:
Nodes are nearly aligned with Sun and Earth
the phase of Moon is new or ful
Precession is caused by
gravitational tugs from sun and moon that try to straighten out its rotational axis
total lunar eclipse
moon passes entirely through umbra
sun, earth, and moon nearly perfectly aligned
partial lunar eclipse
part of the moon passes through umbra
alignment somewhat less perfect
penumbral lunar eclipse
moon passes through penumbra
total solar eclipse
Moon is relatively close to Earth in its orbit; umbra touches a small area of Earth's surface. anyone within this area will see a total solar eclipse.
partial solar eclipse
occurs in lighter area surrounding area of totality that falls within moon's penumbral shadow. only part of sun is blocked from view.
annular eclipse
Moon is relatively far from Earth, in region behind umbra you will see annular eclipse. sunlight surrounds disk of moon. (anyone in surrounding penumbral shadow will see partial solar eclipse).
eclipse seasons
two periods each year when nodes of Moon's orbit are nearly aligned with Sun
saros cycle
eclipses occur in roughly 18 year cycles
how does night sky change throughout the year?
the visible constellations at a particular time of night depend on where earth is located in its orbit around the sun
why do we see phases of moon?
at any time, half the moon is illuminated by the sun and half is in darkness. the face of the moon that we see is some combination of these two portions, determined by the relative locations of the sun, earth, and moon.
what conditions are necessary for an eclipse?
an eclipse can occur only when nodes of moon's orbit are nearly aligned with sun and earth. when this condition is met, we can get a solar eclipse at new moon and a lunar eclipse at full moon.
retrograde motion?
occurs over a few weeks to a few months as earth passes planet in its orbit. greeks rejected this explanation because they couldn't detect stellar parallax because they didn't believe stars were that far away.
Ptolemy
made a model of geometric universe with accurate predictions of planetary positions
copernicus
created sun-centered model of solar system designed to replace ptolemaic model, but it was no more accurate because he still used perfect circles.
tycho
provided observations used by kepler to refine the model by introducing elliptical orbit
saw supernova and comet--cosmos not perfect
galileo
experiments and telescopic observations (telescope saw stars were far away, observed moons orbiting jupiter, saw venus going through phases in a way that proved it must orbit sun and not earth, proved heavens were not perfect) overcame objections of earth orbiting sun.
kepler's laws
1. orbit of each planet is an ellipse with the sun at one focus 2. as a planet moves around its orbit, it sweeps out equl areas in equal times. 3. more distant planets orbit the sun at slower average speeds, following a precise mathematical relationship p^2=a^3. p is planet's orbital period in yrs and a is avg dist from sun in AU
hallmarks of science
1. seeks explanations for observed phenomena that rely solely on natural causes. 2. progresses thru creation and testing of models of nature that explain the observations as simply as possible. 3. scientific model must make testable predictions about natural phenomena that would force us to revise or abandon model if the predictions do not agree w/ observations.
scientific method
observations -> question -> hypothesis -> prediction -> test. if test supports hyp, made additional predictions and test, if it doesn't, revise or abandon hypothesis
kinetic energy
ke=1/2mv^2
energy of motion
potential energy
energy being stored for possible later conversion into kinetic energy. gasoline has chemical p.e. which a car engine converts to k.e. of moving car, etc.
radiative energy
energy carried by light
temperature
avg k.e. of particles. higher temp, particles are moving faster
thermal energy
energy contained within a substance as measured by its temperature. collective k.e. of the many individual particles moving within a substance. depends on both the temperature and the total number of particles. astronauts get cold in space despite high temp b/c of low density of space--few particles are available to transfer thermal energy to them.
law of conservation of energy
energy cannot be created or destroyed
all actions in universe involve exchanges of energy or conversion of energy from one form to another
1/2mv^2-GMm/r < 0
motion is bound (circle, ellipse) because if r got too large the constant would no longer be negative
> 0
motion unbound (escapes!) b/c r can go to infinity
= 0
escape velocity v^2=2GM/r (doesn't depend on m!)
atomic number
number of protons in nucleus
atomic mass number
combined number of protons and neutrons
isotopes
versions of an element with different numbers of neutrons
phases of matter
1. solid: below 0 C, K.E. is low and molecule is bound tightly to neighbor.
2. liquid: temp increases, rigid arrangement vibrates, molecules break bonds to make loose bond.
3. gas: water molecule breaks free of all bonds (molecular dissociation) and moves independently of other molecules
4. plasma: hot gas, atoms ionized (electrons stripped, escaped)
ground state
electron is smeared out to minimum extent that nature allows, atom contains smallest possible amount of electrical potential energy
excited state
electron gains energy, becomes smeared out over a greater volume. become ionized if it gains enough energy and escapes.
how is temperature different from heat?
temperature is a measure of the avg k.e. of the many individual atoms or molecules in a substance. heat depends on both temp and density: at a particular temp, a denser substance contains more thermal energy
what is gravitational potential energy?
energy that can be released by an object falling under the force of gravity. the amt of an object's g.p.e. depends on its mass, the strength of gravity, and how fair it could fall. -GMm/r
what is the difference between speed, velocity, and acceleration?
speed is the rate at which an object is moving. velocity is speed in a certain direction. acceleration is a change in velocity, meaning a change in either speed or direction.
how can you tell when a net force is acting on an object?
a net force must be acting whenever the object's momentum is changing. momentum = mass x velocity
newton's three laws of motion
1. in the absence of a net force acting upon it, an object moves with constant velocity. 2. F=ma. 3. for any force, there is always an equal and opposite reaction force. momentum =mxv
universal law of gravitation
force of gravity is directly proportional to product of the objects' masses and declines with the square of distance btwn two centers. F=Gm1m2/d^2
measure of force of gravity upon you
f=GM(earth)m(you)/r(earth)^2
bound orbits/unbound orbits
ellipses, circles/parabolas=, hyperbolas>
newton's update of kepler's first law
mass
mass potential energy
amount of matter in object
energy is stored in matter itself. mass-energy is what would be released if an amount of mass, m, were converted into energy. e=mc^2
weight
a measurement of the force which acts upon an object. when you freefall, you are weightless.
force
anything that can cause a change in an object's movement
(conservation of) angular momentum
torque
momentum involved in spinning mxvxr
velocity increases when radius decreases
a torque is anything that can cause a change in an objects angular momentum (twisting force). depends on where you apply force.
in absence of net torque, the total angular momentum of a system remains constant
m1v1 + m2v2 = constant conservation of momentum
causes moon to more farther away from Earth. Moon gains angular momentum because earth is being retarded--moon going away from us.
why are there two high tides on earch each day?
the moon's gravity stretches earth along the earth-moon lineso that it bulges both toward and away from the moon
why are tides on earth caused primarily by the moon rather than by the sun?
earth's gravitational attraction to the sun is stronger, but tides are caused by the difference btwn th strength of the gravitational attraction across earth's diameter. This difference is greater for the gravitational force due to the moon because the moon is so much closer than the sun.
why is earth's rotation gradually slowing down?
tidal friction, caused by the way the tidal bulges exert drag on Earth, causes a gradual slowing of Earth's rotation. A related consequence of tidal friction is the Moon's increasing distance from Earth.
Why does the Moon always show the same face to Earth?
the moon's synchronous rotation is a result of tidal forces. The moon may once have rotated much faster, but tidal friction slowed its rotation until it became synchronous with its orbit, at which point tidal friction could not slow the orbit any further.
spring tide
when sun and moon pull in same direction (new and full phases), high tide is higher than usual
neap tide
when sun and moon pull at right angles (first and last quarter phases) high tide is lower than usual