Physics

• acceleration


  The rate of change of velocity, a vector quantity
• acceleration of free fall


  The rate of change of velocity of an object falling in a gravitational field, symbol g
• air resistance


  The drag or resistive force experienced by objects moving through air
• ammeter


  A device used to measure electric current — it must be placed in series and ideally have zero resistance
• ampère


  The base SI unit of electric current, symbol A, defined as the current flowing in two parallel wires in a vacuum 1 m apart such that there is an attractive force of 2.0 × 10−7 N per metre length of wire between them
• amplitude (waves)


  The maximum displacement from the equilibrium position (can be positive or negative)
• angle of incidence


  The angle between the direction of travel of an incident wave and the normal at a boundary between two media
• angle of reflection


  The angle between the direction of travel of a reflected wave and the normal at a boundary between two media
• anion


  A negatively charged ion, one which is attracted to an anode
• anode


  A positively charged electrode
• antiparallel (vectors)


  In the same line but opposite directions
• antiphase


  Particles oscillating completely out of step with each other (one reaches its maximum positive displacement as the other reaches its maximum negative displacement) are in antiphase
• Archimedes' principle


  The upthrust on an object in a fluid is equal to the weight of fluid it displaces
• average speed


  The rate of change in distance calculated over a complete journey
• average velocity


  The change in displacement Δs for a journey divided by the time taken Δt
• base unit


  One of seven units that form the building blocks of the SI measurement system
• battery


  A collection of cells that transfers chemical energy into electrical energy
• braking distance


  Distance travelled by a vehicle from the time the brakes are applied until the vehicle stops
• breaking strength


  The stress value at the point of fracture, calculated by dividing the breaking force by the cross-sectional area
• brittle


  Property of a material that does not show plastic deformation and deforms very little (if at all) under high stress
• capacitor


  A component that stores charge, consists of two plates separated by an insulator (dielectric)
• cathode


  A negatively charged electrode
• cation


  A positively charged ion, one which is attracted to a cathode
• cell


  A device that transfers chemical energy into electrical energy
• centre of gravity


  An imaginary point at which the entire weight of an object appears to act
• centre of mass


  A point through which any externally applied force produces straight-line motion but no rotation
• charge carrier


  A particle with charge that moves through a material to form an electric current — for example, an electron in a metal wire
• closed system


  An isolated system that has no interaction with its surroundings
• coherence


  Two waves sources, or waves, that are coherent have a constant phase difference
• component


  One of the two perpendicular vectors obtained by resolving a vector
• compression


  The decrease in length of an object when a compressive force is exerted on it
• compression (waves)


  A moving region in which the medium is denser or has higher pressure than the surrounding medium
• compressive deformation


  A change in the shape of an object due to compressive forces
• compressive force


  Two or more forces together that reduce the length or volume of an object
• conservation of charge


  A conservation law which states that electric charge can neither be created nor destroyed — the total charge in any interaction must be the same before and after the interaction
• constant speed


  Motion in which the distance travelled per unit time stays the same
• constant velocity


  Motion in which the change in displacement per unit time stays the same
• constructive interference


  Superposition of two waves in phase so that the resultant wave has greater amplitude than the original waves
• conventional current


  A model used to describe electric current in a circuit — conventional current travels from positive to negative — it is the direction in which positive charges would travel
• coulomb


  The derived SI unit of electrical charge, symbol C — 1 coulomb of electric charge passes a point in one second when there is an electric current of one ampere, 1 C = 1 A s