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116 Cards in this Set
- Front
- Back
speed |
the rate at which an object moves. Its units are distance divided by time
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velocity |
the combination of speed and direction of motion; it can be stated as a speed in a particular direction
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acceleration |
the rate at which an object's velocity changes
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acceleration due to gravity |
the acceleration of a falling object. on Earth, the acceleration due to gravity is 9.8 m/s^2
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momentum |
the product of an object's mass and velocity
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force |
anything that can cause a change in momentum
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net force |
the overall force to which an object responds; the net force is equal to the rate of change in the object's momentum, or equivalently to the object's mass x acceleration |
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angular momentum |
momentum attributable to rotation or revolution. the angular momentum of an object moving in a circle of radius r is the product m x v r
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mass |
a measure of the amount of matter in an object
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weight |
the net force that an object applies to its surroundings; in the case of a stationary body on the surface of Earth, it equals mass x acceleration of gravity
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rotational angular momentum |
angular momentum due to the Earth's rotation |
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orbital angular momentum |
angular momentum due to Earth's orbit around Sun |
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torque |
a twisting force that can cause a change in an object's angular momentum
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free-fall |
the condition in which an object is falling without resistance; objects are weightless when in free-fall
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weightless |
a weight of zero, as occurs during free-fall
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Newton's 1st Law |
an object moves at a constant velocity if there is no net force acting upon it |
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Newton's 2nd Law |
F=ma force = rate of change in momentum |
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Newton's 3rd Law |
For any force, there is always an equal and opposite reaction force |
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conservation of momentum |
the principle that, in the absence of a net force, the total momentum of a system remains constant |
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conservation of angular momentum |
the principle in that, in the absence of a net torque, the total angular momentum of a system remains constant |
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conservation of energy |
the principle that energy can be neither created nor destroyed, but can only change from one form to another |
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kinetic energy |
- energy of motion - 1/2 mv^2 |
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radiative energy |
energy carried by light; the energy of a photon is Planck's constant times its frequency - E = hf |
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potential energy |
energy stored for later conversion into kinetic energy; includes gravitational potential energy, electric potential energy, and chemical potential energy |
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joule |
the international unit of energy, equivalent to about 1/4000 of a calorie |
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thermal energy |
- the collective kinetic energy, as measured by temperature, of the many individual particles moving with a substance - total kinetic energy |
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temperature |
- a measure of the avg. kinetic energy of particles in a substance - average kinetic energy |
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Kelvin |
the most commonly used temperature scale in science, defined such that absolute zero is 0 K and water freezes at 273.15 K |
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gravitational potential energy (GPE) |
energy that an object has by virtue of its position in a gravitational field; an object has more gravitational potential energy when it has a greater distance that it can potentially fall |
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mass-energy |
the potential energy of mass, which has an amount E = mc^2 |
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orbital energy |
the sum of an orbiting object's kinetic and GPE's |
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gravitational encounter |
an encounter in which two or more objects pass near enough so that each can feel the effects of the other's gravity and they can therefore exchange energy |
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escape velocity |
the speed necessary for an object to completely escape the gravity of a large body such as a moon, planet, or star |
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tidal force |
a force that occurs when the gravity pulling on one side of an object is larger than that on the other side, causing the object to stretch |
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tidal friction |
friction within an object that is caused by a tidal force |
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power |
the rate of energy usage, usually measured in watts |
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watts |
the standard unit of power, 1 joule/s |
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diffraction grating |
a finely etched surface that can split light into a spectrum |
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emission |
the process by which matter emits energy in the form of light |
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absorption |
the process by which matter absorbs radiative energy |
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transmission |
the process in which light passes through matter without being absorbed |
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reflection/scattering |
the process by which matter changes the direction of light |
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wavelength |
the distance between adjacent peaks of a wave |
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frequency |
the rate at which peaks of a wave pass by a point, measured in units of 1/d, often cycles per second or hertz |
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cycles per second |
units of frequency for a wave; describes the number of peaks or troughs of a wave that pass by a given point each second |
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hertz |
standard unit of frequency for light waves, 1/s |
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field |
an abstract concept used to describe how a particle would interact with a force |
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electromagnetic wave |
a synonym for light, which consists of waves of electric and magnetic fields |
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speed of light |
300,000 km/s |
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photons |
an individual particle of light, characterized by a wavelength and a frequency |
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electromagnetic spectrum |
the complete spectrum of light |
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electromagnetic radiation |
another name for light of all types on the spectrum |
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visible light |
the light our eyes can see ranging from 400 to 700 nm |
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microwaves |
generally considered a subset of radio waves |
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atoms |
a nucleus made from protons and neutrons, surrounded by a cloud of electrons |
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element |
a substance made from individual atoms of a particular atomic number |
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protons |
particles found in atomic nuclei with positive charge, made of three quarks |
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neutrons |
no electrical charge, built from three quarks |
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electrons |
fundamental particles with negative charge, distribution of electrons gives atoms size |
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nucelus |
compact center made from protons and neutrons |
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electrical charge |
a property of matter that is described by its amount and as either positive or negative; more technically, a measure of how a particle responds to electromagnetic force |
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atomic number |
the number of protons in an atom |
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atomic mass number |
combined number of protons and neutrons in an atom |
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isotopes |
forms of an element that have the same number of protons but different numbers of neutrons |
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molecules |
combinations of two or more atoms held together by chemical bonds |
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phase |
state determined by the way in which atoms or molecules are held together |
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solid |
atoms or molecules are held rigidly in place |
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liquid |
atoms or molecules are held together but move freely |
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gas |
atoms or molecules can move essentially independent of one another |
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chemical bond |
interactions between electrons that hold atoms in a molecule together |
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sublimation |
atoms or molecules escape into the gas phase from a solid |
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evaporation |
from liquid to gas phase |
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molecular dissociation |
a molecule splits into its component atoms |
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ions |
atoms with a positive or negative charge |
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ionization |
the process of stripping an electron from an atom |
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plasma |
gas consisting of ions and electrons |
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pressure |
force per unit area pushing on an object |
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energy levels |
possible energies of an electron in an atom |
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energy level transitions |
an electron can rise from a lower level to a higher one or fall from high to low |
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spectroscopy |
process of obtaining spectra from astronomical objects |
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intensity |
measure of the amount of energy coming from light of a specific wavelength |
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continuous spectrum |
a spectrum that spans a broad range of wavelengths without interruption by emission or absorption lines |
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emission lines |
what indicate different lights on a spectrum |
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emission line spectrum |
a spectrum that contains emission lines |
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absorption lines |
what appears when certain wavelengths of light are captured |
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absorption line spectrum |
a spectrum that contains absorption lines |
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molecular bands |
tightly bunched lines in an object's spectrum that are produced by molecules |
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thermal radiation |
spectrum of radiation produced by an opaque object that depends only on the object's temperature; sometimes called blackbody radiaton |
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Two Laws of Thermal Radiation |
1. each square meter of a hotter object emits more light at all wavelengths 2. Wien's law - hotter objects emit photons with a higher average energy |
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Doppler Effect |
the effect that shifts the wavelengths of spectral features in objects that are moving toward or away from the observer |
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blueshift |
shorter wavelengths from Doppler Effect, object moving toward observer |
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redshift |
longer wavelengths from Doppler Effect, object moving away from observer |
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focal point (focus) |
the point at which rays of light that were initially parallel converse (such as those from a distant star) |
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focal plane |
the place where an image created by a lens or mirror is in focus |
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detector |
the place on a camera where light is recorded into a permanent image |
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exposure time |
the amount of time during which light is collected to make a single image |
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pixels |
and individual "picture element" on a CCD (Charge Coupled Device - type of electronic light detector) |
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light-collecting area |
the area of the primary mirror or lens that collects light in a telescope |
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angular resolution |
the smallest angular separation that two pointlike objects can have an sill be seen as distinct points of light (rather than as a single point of light) |
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diffraction limit |
the angular resolution that a telescope could achieve if it were limited only by the interference of light waves; it is smaller for larger telescopes |
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refracting telescope |
a telescope that uses lenses to focus light |
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reflecting telescope |
a telescope that uses mirrors to focus light |
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spectrographs |
an instrument used to record spectra |
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light curves |
a graph of an object's intensity against time |
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light pollution |
human-made light that hinders astronomical observations |
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turbulence |
rapid and random motion |
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adaptive optics |
a technique in which telescope mirrors flex rapidly to compensate for the bending of starlight caused by atmosphere turbulence |
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grazing incidence mirrors |
reflections in which light grazes a mirror surface and is deflected at a small angle; commonly used to focus high-energy ultraviolet light and x rays |
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interferometry |
a telescopic technique in which two or more telescopes are used in tandem to produce much better angular resolution than the telescopes could achieve individually |
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image |
a picture of an object made by focusing light |
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inverse square law |
a law stating that the intensity of an effect such as illumination or gravitational force changes in inverse proportion to the square of the distance from the source. |
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universal law of gravitation |
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unbound orbit |
hyperbola, parabola, paths that bring an object close to another object just once |
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bound orbit |
ellipse, orbit in which an object goes around another object over and over again |
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center of mass |
the point at which two objects would balance if they were somehow connected |
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Newton's Version of Kepler's Third Law |
objects' characteristics tell us the masses of distant objects |