Physics
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159 terms
Terms | Definitions |
|---|---|
 distance | how far an object has moved |
| displacement | distance and direction of an object's change in position |
| speed | distance an object travels per unit of time |
| average speed | total distance traveled divided by the total time of travel |
| instantaneous speed | speed at a given point in time |
| velocity | speed and direction of an object's motion--measured in meters per second |
| acceleration | rate of change in velocity--measured in meters per second squared |
| force | push or pull on an object |
| net force | the sum of the forces that are acting on an object |
| balanced forces | forces equal in size and opposite in direction |
| inertia | tendency of an object to resist any change in its motion |
| friction | force that opposes the sliding motion of two surfaces that are touching each other |
| static friction | frictional force that prevents two surfaces from sliding past each other |
| sliding friction | force that opposes two surfaces sliding past each other |
| air resistance | opposes the motion of objects that move through the air |
| gravity | attractive force between any two objects that depends on masses of objects and distance between them |
| weight | gravitational force exerted on an object |
| centripetal acceleration | acceleration toward the center of a curved or circular path |
| centripetal force | net force exerted toward the center of a curved path |
| momentum | product of an object's mass and velocity--measured in kilogramsmeters per second (kgm/s) |
| kinetic energy | energy a moving object has because of its motion |
| joule | unit of energy |
| potential energy | stored energy due to position |
| elastic potential energy | energy stored by something that can stretch or compress |
| chemical potential energy | energy stored in chemical bonds |
| gravitational potential energy | energy stored by objects due to their position above earth's surface |
| mechanical energy | total amount of potential and kinetic energy in a system |
| law of conservation of energy | energy cannot be created or destroyed |
| thermal energy | sum of kinetic and potential energy in all the particles in an object |
| temperature | measure of the average kinetic energy of the particles in the object |
| heat | thermal energy that flows from something at a higher temperature to something at a lower temperature |
| specific heat | amount of heat needed to raise temperature of 1 kg of some material by 1 Celsius |
| conduction | transfer of thermal energy by collisions between particles in matter |
| convection | transfer of thermal energy in a fluid by the movement of warmer and cooler fluid from place to place |
| radiation | transfer of energy by electromagnetic waves |
| insulator | material in which heat flows slowly |
| solar collector | device used in an active solar heating system that absorbs radiant energy from the Sun. |
| first law of thermodynamics | increase in thermal energy of a system=work done on the system plus heat transferred to the system |
| second law of thermodynamics | it's impossible for heat to flow from a cool object to a warmer object unless work is done |
| heat engine | any device that converts heat into work |
| internal combustion engine | an engine that burns fuel inside cylinders within the engine |
| static electricity | accumulation of excess electric charge on an object |
| law of conservation of charge | charge can be transferred from object to object, but it can't be created or destroyed |
| conductor | material in which electrons are able to move easily |
| insulator | material in which electrons are not able to move easily |
| charging by contact | process of transferring charge by touching or rubbing |
| charging by induction | the rearrangement of electrons on a neutral object caused by a nearby charged object |
| electric current | net movement of electric charges in a single direction |
| voltage difference | related to force that causes electric charges to flow--measured in volts |
| circuit | closed path that electric current follows |
| resistance | tendency for a material to oppose flow of electrons, changing electrical energy into thermal energy and light--measured in ohms |
| Ohm's law | current in circuit=voltage difference divided by resistance |
| series circuit | a circuit in which all parts are connected in a single loop |
| parallel circuit | a closed electrical circuit in which the current is divided into two or more paths and then returns via a common path to complete the circuit |
| electric power | the rate at which electrical energy is converted to another form of energy |
| magnetism | refers to properties and interactions of magnets |
| magnetic field | exerts force on other magnets and objects made of magnetic materials |
| magnetic poles | where magnetic force exerted by magnet is strongest |
| magnetic domains | groups of atoms with aligned magnetic poles |
| electromagnet | a temporary magnet made by coiling wire around an iron core |
| solenoid | single wire wrapped into a cylindrical wire coil |
| galvanometer | instrument that uses an electromagnet to measure electric current |
| electric motor | device that changes electrical energy into mechanical energy |
| electromagnetic induction | the process of creating a current in a circuit by changing a magnetic field |
| generator | uses electromagnetic induction to transform mechanical energy to electrical energy |
| turbine | large wheel that rotates when pushed by wind, water, or steam |
| direct current (DC) | current in which the electrons move in one direction |
| alternating current (AC) | current in which the electrons move back and forth |
| transformer | device that increases or decreases the voltage of an alternating current |
| step up transformer | transformer that increases the voltage so that the output voltage is greater than the input voltage |
| step down transformer | transformer that decreases the voltage so that the output voltage is less than the input voltage |
| wave | repeating disturbance or movement that transfers energy through matter or space |
| medium | matter waves travel through |
| transverse wave | matter in medium moves back and forth at right angles |
| compressional waves | matter in medium moves back and forth along same direction wave travels |
| crests | alternating high points in a wave |
| troughs | alternating low points in a wave |
| rarefaction | less-dense region of a compressional wave |
| wavelength | distance between 1 point on a wave and the nearest point just like it |
| frequency | the number of wavelengths that pass a fixed point each second |
| period | amount of time it takes 1 wavelength to pass a point |
| amplitude | related to the energy carried by a wave |
| refraction | bending of a wave caused by a change in its speed as it moves from one medium to another |
| diffraction | occurs when an object causes a wave to change direction and bend around it |
| interference | when 2 or more waves overlap and combine to form a new wave |
| standing wave | the resultant of two wave trains of the same wavelength, frequency and amplitude, traveling in opposite directions through the same medium |
| resonance | process by which an object is made to vibrate by absorbing energy at its natural frequencies |
| eardrum | the membrane in the ear that vibrates to sound |
| cochlea | the snail-shaped tube (in the inner ear coiled around the modiolus) where sound vibrations are converted into nerve impulses by the Organ of Corti |
| intensity | the amount of energy that flows through a certain area in a given amount of time |
| loudness | human perception of sound intensity |
| decibel | unit for sound intensity |
| ultrasonic waves | sound frequencies above 20,000 Hz |
| Doppler effect | change in pitch or wave frequency due to a moving wave source |
| music | made of sounds deliberately used in a regular pattern |
| sound quality | Differences among sounds of the same pitch and loudness |
| overtone | a natural frequency that is a multiple of the fundamental tone's frequency |
| resonator | hollow chamber that amplifies sound when air is vibrated |
| acoustics | the study of the physical properties of sound |
| echolocation | process of which objects are located by emitting sounds and interpreting sound waves that are reflected back |
| sonar | a system that uses sound waves to measure distances and locate objects. |
| electromagnetic waves | made by vibrating electric charges; can travel through space where matter is not present |
| radiant energy | energy carried by electromagnetic wave |
| photon | an electromagnetic wave that behaves as a particle |
| radio waves | low-frequency electromagnetic waves with wavelengths longer than about 1 millimeter |
| microwaves | radio waves with wavelengths of less than about 30 cm |
| infrared waves | type of electromagnetic wave with wavelengths between about 1 mm and about 750 billionths of a meter |
| visible light | Electromagnetic radiation that can be seen with the unaided eye |
| ultraviolet waves | electromagnetic waves with wavelengths from about 400 billionths to 10 billionths of a meter |
| X rays | have wavelengths between about ten billionths and ten trillionths of a meter |
| gamma rays | electromagnetic waves shorter than about 10 trillionths of a meter are gamma rays |
| carrier wave | specific frequency a radio station is assigned |
| cathode-ray tube | sealed vacuum tube in which 1 or more beams of electrons are produced |
| transceiver | transmits 1 radio signal and receives another radio signal from a base unit |
| GPS (Global Positioning System) | system of satellites, ground monitoring stations, and receivers that determine your exact location at or above earth's surface |
| opaque | only absorbs and reflects light; no light passes through it |
| translucent | material that allows some light to pass through it; can't see clearly through translucent materials |
| transparent | transmit all light striking object; can see clearly |
| index of refraction | property of the material that indicates how much the speed of light in the material is reduced |
| mirage | image of a distant object produced by the refraction of light through air layers of different densities |
| pigment | colored material used to change color of other substances |
| incandescent light | generated by heating a piece of metal until it glows |
| fluorescent light | uses phosphors to convert ultraviolet radiation to visible light |
| sodium-vapor lights | used for streetlights and other outdoor lighting; contains a tube with a mixture of neon gas, argon gas, and sodium metal |
| tungsten-halogen lights | sometimes used to create intensely bright light |
| coherent light | light of only 1 wavelength that travels with its crests and troughs aligned |
| incoherent light | can contain more than 1 wavelength, and its electromagnetic waves are not aligned |
| polarized light | waves vibrate in only one direction |
| holography | technique that produces a hologram--a complete three-dimensional photographic image of an object |
| total internal reflection | occurs when light strikes a boundary between two materials and is completely reflected |
| plane mirror | a smooth, flat mirror |
| virtual image | an image the brain perceives even though no light passes through it |
| concave mirror | mirror's surface is curved inward |
| optical axis | imaginary straight line drawn perpendicular to the surface of the mirror at its center |
| focal length | distance from center of mirror to focal point |
| real image | formed when light rays converge to form the image |
| convex mirror | mirror that curves outward |
| convex lens | thicker in the middle than at the edges |
| concave lens | thinner in the middle; thicker at edges |
| cornea | transparent covering on eyeball which light enters through |
| retina | inner lining of your eye |
| refracting telescope | uses 2 convex lenses |
| reflecting telescope | uses concave mirror, plane mirror, and convex lens |
| microscope | uses 2 convex lenses with short focal lengths to magnify small close objects |
| strong force | causes protons and neutrons to be attracted to each other |
| radioactivity | process of nuclear decay |
| alpha particle | made of 2 protons and neutrons(also known as 4-2 He) |
| transmutation | process of changing one element to another through nuclear decay |
| beta particle | electron emitted from the nucleus |
| gamma rays | electromagnetic waves with the highest frequencies and the shortest wavelengths in the electromagnetic spectrum |
| half-life | amount of time it takes for half the nuclei in a sample of the isotope to decay |
| cloud chamber | used to detect alpha or beta particle radiation; filled with water or ethanol vapor |
| bubble chamber | holds superheated liquid; doesn't boil because pressure in chamber is too high |
| Geiger counter | device that measures amount of radiation by producing electric current when it detects a charged particle |
| nuclear fission | process of splitting a nucleus into several smaller nuclei |
| chain reaction | series of repeated fission reactions caused by release of neutrons in each reaction |
| critical mass | amount of material required to maintain chain reaction |
| nuclear fusion | two nuclei with low masses combine to form one nucleus of larger mass |
| tracer | a radioisotope used to find or keep track of molecules in an organism |
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