# Active Physics Vocabulary Table (2004)

 acceleration The rate at which an object's velocity changes with time. It involves a change in the speed (increase or decrease) OR direction OR both speed and direction. amplitude The height of the wave centimeter A unit of measure in the metric system of measurement equivalent to 1/100 of a meter or 0.3927 inch; abbreviated is cm. centripetal force The force making a motion is a circle possible, always directed to the center of the circle constructive interference When waves align and the resulting wave has troughs and humps that are larger. controlled variable An object or condition you want to remain constant when you carry out a scientific investigation. destructive interference When waves align and the resulting wave has troughs and humps that are smaller. electromagnetic Relating to the interplay between electric and magnetic fields. In particular, light (as well as x-rays, microwaves, gamma rays, etc.) electromagnetic waves Radiation consisting of waves of energy sent through space and matter associated with electric and magnetic fields resulting from the acceleration of an electric charge force Push or pull that gives energy to an object, sometimes causing a change in the motion of the object. frame of reference Any system for specifying the precise location of objects in space frequency The number of back-and-forth cycles per second, in a wave or wave-like process. friction A force that resists motion between two objects in contact. g A unit of mass gravitational field Field created by any object with mass, extending outward in all directions, which determines the influence of that object on all others. Heat The transfer of energy from one object at a higher temperature to another object at a lower temperature. hologram Laser-generated image with three-dimensional properties inertia The tendency of matter to remain at rest if at rest or to remain in motion in a straight line if in motion. kgm/s2 The base units that make up a Newton (a unit of force) kinetic energy The energy possessed by a moving object. = ½ mv2 longitudinal waves A wave in which the individual particles of a medium vibrate back and forth in the direction in which the wave travels. Sound is this type of wave m A unit of length equal to 1 meter m/s A unit of speed meters per second m/s2 A unit of acceleration meters per second squared manipulated variable Object or condition that you change on purpose to test your hypothesis mass A measure of how much material something contains. This shouldn't be confused with weight, which is a measure of the force of gravity on an object. mechanical waves Waves which travel through a medium Sound waves, water waves and waves in solid objects meter The standard unit of length in the SI system of measure that equals 39.37 inches. momentum Mass times velocity; a quantity that determines the potential force that an object can impart to another object by collision motion A change in the position or location of one thing with respect to another net force Sum of all the forces acting on an object photovoltaic cell An electronic device consisting of layers of semiconductor materials that is capable of converting light directly into electricity. potential energy Stored energy of a material, a result of its position in an electric, magnetic, or gravitational field PE=mgh primary or P waves, P waves, or compressional wave, are seismic body waves that shakes the ground back and forth in the same direction as the direction the wave is moving. reflection The change in direction (or return) of waves striking a surface refraction Waves change direction as they pass from one medium to another. responding variable Object or condition that changes when you change the manipulated variable in a scientific investigation. secondary or S S waves, are seismic body waves that shakes the ground back and forth perpendicular to the direction the waves are moving SI system A complete system of units of measurement for scientists; fundamental quantities are length (meter) and mass (kilogram) and time (second) and electric current (ampere) and temperature (Kelvin) and amount of matter (mole) and luminous intensity (candela) slope of graph The mathematical result of the change in the y axis of a line divided by the corresponding change on the x axis sound Mechanical energy vibrations transmitted as waves through a solid, liquid, or a gas that can be detected by the human ear speed Distance traveled per unit time speed of light The speed at which electromagnetic radiation propagates in a vacuum; it is defined as 299 792 458 m/s standing wave A wave that appears to be standing still; it occurs when waves with the same frequency (and wavelength) moving in opposite directions interfere with each other subsystem A major part of a system which itself has the characteristics of a system system Group of interacting, interrelated, or interdependent parts made up of matter and energy that form a complex whole thermal energy Energy in the form of heat. The total internal kinetic and potential energy of an object due to the random motion of its atoms and molecules. thought experiment An experiment that cannot be or is not carried out in practice; it is reasoned through by thought and intuition. transverse waves A wave in which the vibrations of the medium are perpendicular to the direction the wave is moving unbalanced force A force that is not countered by another force in the opposite direction. vector A measurement having both magnitude and direction, velocity, acceleration and force It may be represented as a directed line segment velocity Rate of change of position or direction of an object wave crest The highest part of a wave. The curved tops or ridges of an oscillating wave. wave interference The superposition (overlapping) of two or more waves resulting in a new wave pattern wave medium The material that can carry a mechanical wave wave period The time elapsed for a wave to travel the distance of one wavelength. wave speed The velocity of a traveling wave wave superposition The addition of two or more waves to produce a new wave. wave trough The lowest part of a wave, between successive crests wavelength The distance measured from crest to crest of one complete wave or cycle. weight The force of gravity acting on a body, equal to the mass of the body multiplied by the acceleration of gravity work The transfer of energy from one object or system to another by applying a force over a distance. The formula is (force) x (distance).