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Glossary: Unit I APS.SE.Backmatter 9/1/04 10:46 AM Page 833 Glossary Glossary: Unit I Chapters 1–9 center of mass: the point at which all the mass of an object is considered to be Active Physics concentrated for calculations concerning motion of the object. acceleration: the change in velocity per unit time. centripetal acceleration: the inward radial ⌬v acceleration of an object moving at a a ϭ ᎏ ⌬t constant speed in a circle. air resistance: a force by the air on a moving v2 a ϭ ᎏ object; the force is dependent on the speed, R volume, and mass of the object as well as on centripetal force: a force directed towards the properties of the air, like density. the center that causes an object to follow a alternating current: an electric current that circular path. reverses in direction. mv2 F ϭ ᎏᎏᎏ R amplitude: the maximum displacement of a closed system: a physical system on which particle as a wave passes; the height of a no outside influences act; closed so that wave crest; it is related to a wave’s energy. nothing gets in or out of the system and ampere: the SI unit for electric current; one nothing from outside can influence the ampere (1 A) is the flow of one coulomb of system’s observable behavior or properties. charge every second. concave lens: a lens that causes parallel light analog: a description of a continuously rays to diverge; a lens that is thicker at its variable signal or a circuit; an analog signal edges than in the center. can be represented as a series of waves. conduction: (of heat) the energy transfer angle of incidence: the angle a ray of light from one material or particle to another makes with the normal to the surface at the when the materials or particles are in direct point of incidence. contact. angle of reflection: the angle a reflected ray constructive interference: the result of makes with the normal to the surface at the superimposing different waves so that two point of reflection. or more waves overlap to produce a wave with a greater amplitude. antinode: a point on a standing wave where the displacement of the medium is at its convection: the heat transfer resulting from maximum. the movement of the heated substance, such as air or water currents. atom: the smallest particle of an element that has all the element’s properties; it converging lens: parallel beams of light consists of a nucleus surrounded by passing through the lens are brought to a real electrons. point or focus (convex lens) (if the outside index of refraction is less than that of the lens atomic mass unit: a standard unit of atomic material.); also called a convex lens. mass based on the mass of the carbon atom, which is assigned the value of 12. convex lens: a lens that causes parallel light rays to converge (if the outside index of baryon: a group of elementary particles that refraction is less than that of the lens are affected by the nuclear force; neutrons material); a lens that is thinner at its edges and protons belong to this group. than in the center. 833 Active Physical Science APS.SE.Backmatter 9/1/04 10:46 AM Page 834 Glossary Unit 1 Chapters 1–9 Active Physics coulomb: the SI unit for electric charge; one electrical resistance: opposition of a material coulomb (1 C) is equal to the charge of 6.25 to the flow of electrical charge through it: it x 1018 electrons. is measured in ohms (Ω); the ratio of the potential difference to the current. Coulomb’s Law: the relationship among V R ϭ ᎏ electrical force, charges, and the distance I between the charges. electromagnet: a device that uses an electric q q ϭ ᎏᎏ1 2 F k 2 current to produce a concentrated magnetic d field. crest: the highest point of displacement of a wave. electromagnetic waves: transverse waves that are composed of perpendicular electric and critical angle: the angle of incidence for magnetic fields that travel at 3 x 108 m/s in which a light ray passing from one medium a vacuum; examples of electromagnetic to another has an angle of refraction of 90º waves in increasing wavelength are gamma degrees. rays, x-rays, ultraviolet radiation, visible destructive interference: the result of light, infrared radiation, microwaves, and superimposing different waves so that two radio waves. or more waves overlap to produce a wave electron: a negatively charged particle with a with a decreased amplitude. charge of 1.6 x 10-19 coulombs and a mass -31 diffraction: the ability of a wave to spread of 9.1 x 10 kg. out as it emerges from an opening or moves entropy: a measure of the degree of disorder beyond an obstruction. in a system or a substance. digital: a description of data that is stored or focal length: the distance between the center transmitted as a sequence of discrete of a lens and either focal point. symbols; usually this means binary data (1s and 0s) represented using electronic or focus: the place at which light rays converge electromagnetic signals. or from which they appear to diverge after refraction or reflection; also called focal displacement: the difference in position point. between a final position and an initial position; it depends only on the endpoints, force: a push or a pull that is able to not on the path; displacement is a vector; it accelerate an object; force is measured in has magnitude and direction. newtons; force is a vector quantity. Doppler Effect: change in frequency of a frame of reference: a vantage point with wave of light or sound due to the motion of respect to which position and motion may the source or the receiver. be described. electric charge: a fundamental property of free fall: a fall under the influence of only matter; charge is either positive or negative. gravity. electric circuit: an electrical device that frequency: the number of waves produced provides a conductive path for electrical per unit time; the frequency is the reciprocal current to move continuously. of the amount of time it takes for a single wavelength to pass a point. electric current: the flow of electric charges ϭ ᎏv through a conductor; electric current is f ␭ measured in amperes. electric field: the region of electric influence defined as the force per unit charge. 834 Active Physics APS.SE.Backmatter 9/1/04 10:46 AM Page 835 Glossary friction: a force that acts to resist the relative joule: the SI unit for work and all other motion or attempted motion of objects that forms of energy; one joule (1J) of work is are in contact with each other. done when a force of one newton moves an object one meter in the direction of the galvanometer: an instrument used to detect, force. measure, and determine the direction of small electric currents. kinetic energy: the energy an object possesses because of its motion. gravitational potential energy: the energy a 1 body possesses as a result of its position in a KE ϭ ᎏᎏᎏ mv2 2 gravitational field. lepton: a group of elementary particles that GPE ϭ mgh are not affected by the nuclear force; electrons belong to this group. gravity: the force of attraction between two light-year: the distance that light travels in bodies due to their masses. one year (9.46 x 1012 km). heat energy: a form of energy associated longitudinal pulse or wave: a pulse or wave in with the motion of atoms or molecules. which the motion of the medium is parallel Hooke’s Law: the distance of stretch or to the direction of the motion of the wave. compression of a spring is directly magnetic field: the region of magnetic proportional to the force applied to it. influence around a magnetic pole or a F ϭ k∆x moving charged particle. impulse: the product of force and the meson: a virtual particle that mediates the interval of time during which the force acts; strong, nuclear force of an atom; the impulse results in a change in momentum. protons and neutrons exchange mesons; the protons and protons exchange mesons; the impulse ϭ Ft ϭ ∆(mv) neutrons and neutrons exchange mesons. index of refraction: a property of a medium model: a representation of a process, system, that is related to the speed of light through or object. it; it is calculated by dividing the speed of light in vacuum by the speed of light in the momentum: the product of the mass and the medium. velocity of an object; momentum is a vector quantity. inertia: the natural tendency of an object to remain at rest or to remain moving with p = mv constant speed in a straight line. neutron: a subatomic particle that is part of inertial frame of reference: unaccelerated the structure of the atomic nucleus; a point of view in which Newton’s Laws hold neutron is electrically neutral. true. Newton’s Law of Gravitational Attraction: the inverse square relation: the relationship of a relationship among gravitational force, force to the inverse square of the distance masses, and the distance between the from the mass (for gravitational forces) or masses. the charge (for electrostatic forces). Gm m F ϭ ᎏᎏᎏ1 2 2 ionization energy: the energy required to free d an electron from an atom. 835 Active Physical Science APS.SE.Backmatter 9/16/04 4:02 PM Page 836 Glossary Unit 1 Chapters 1–9 Active Physics Newton’s Laws of Motion: open system: a physical system on which outside influences are able to act; open so Newton’s First Law of Motion: an object at that energy can be added and/or lost from rest stays at rest and an object in motion the system.
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