【正文】 n, shape, configuration or state of the system.Power: rate of work done or energy transfer.Pressure: the force acting perpendicularly per unit area.Pressure law: the pressure of a fixed mass of gas at constant volume is directly proportional to the absolute scale of temperature.Principle of moment: the sum of the clockwise moments about a point must be equal to the sum of the anticlockwise moments about the point when the body is in equilibrium.Principle of superposition: whenever two or more waves are travelling in the same region simultaneously, the total displacement at any point is equal to the vector sum of their individual displacement at that point.Process: a change in the thermodynamic variables in a system.Progressive waves。 waves that carry energy from one point to another through oscillation or vibration within the medium.Random errors: unpredictable deviations from the actual value such that each reading has an equal chance to fall above or below the actual value.Random motion: the motion of an atom or molecule in a fluid whose velocity changes in an erratic or unpredictable manner as a result of collisions with other atoms or molecules.Resistance thermometer: a thermometer which relies on the change in resistance of a wire as temperature changes.Resonance: a system oscillates with maximum amplitude when it is subjected to an oscillatory force whose driving frequency is equal to the natural frequency of the system,Resultant: the name given to a vector whose effects are entirely the same as the bined action of two or more vectors.Root mean square speed: the square root of the mean square speed of the molecules of a gas.Scalar quantity: a physical quantity which has magnitude but no direction.Simple harmonic motion: the to and fro motion of a particle about an equilibrium position such that its acceleration is proportional to the displacement from the equilibrium position and is always directed towards that position.Specific heat capacity: the amount of heat required to raise the temperature of 1 kg of a substance through 1K or 1176。C.Specific latent heat of fusion: the quantity of heat required to change 1 kg of a substance from solid state to liquid state without a change in temperature.Specific latent heat of vaporisation: the quantity of heat required to change 1kg of a liquid to vapour without a change in temperature. Speed: distance travelled per unit time. The SI unit of speed is ms. Speedtime graph: displays the variation of speed of an object with time.Stationary wave: a wave formed by the superposition of two waves which are travelling in opposite directions, and which have the same speed, frequency and amplitudes. The resultant wave stores vibrational energy and its wave profile does not move through the medium but remains stationary.Steady state: the condition reached when the temperature of a body attains a constant value when heat gained by the body is equal to heat lost by the body.Steam point: the temperature of steam maintained at standard atmospheric pressure when it is in thermal equilibrium with pure water.System: a welldefined quantity of matter bounded entirely by a real or imaginary surface.Systematic error: an inherent error in an instrument or in a technique which causes a random set of readings to be distributed consistently around an average that is significantly different from the actual value.Temperature: a measure of the degree of hotness of an object.Terminal speed: the constant speed attained by a body when the upward net force acting on it balances the downward weight as it falls freely through a fluid.Thermal equilibrium: a state in which every part of a body attains the same temperature when heat gained by the body is equal to the heat lost by the body.Thermocouple: a thermometer which uses the electromotive force (emf) generated between two dissimilar junctions to measure a difference in temperature.Transverse waves: progressive waves in which the direction of vibrations of the waves is perpendicular to the line of flow of energy.Trough: the lowest point on a wave.Thermodynamics (first law): the heat ⊿Q transferred to a closed system increases its internal energy ⊿U and causes the system to do work ⊿W on its surroundings during the change.Torque: moment of a couple.Triple point: the single temperature at which pure ice, water, and water vapour coexist together in thermal equilibrium,Uncertainty: the spread of values on either side of a measurement,Vector: a physical quantity which has both magnitude and direction.Velocity: the rate of change of displacement.Velocitytime graph: displays the variation of velocity of an object with time.Wavefront: the crest of a wave or a line that Joins all identical points on a wave with the same phase.Wavelength: the distance between two successive crests or two successive troughs.Work done (by a force on a body): the product of the force and the distance moved in the direction of the force.Zero error the systematic error of a measuring instrument when the scale reading of that instrument does not read exactly zero when there is nothing being measured.Zeroth law of thermodynamics: If two bodies X and Y are separately in thermal equilibrium with a third body T, then X and Y are in thermal equilibrium with each other.Glossary of terms used in Physics ⅡAbsorption line spectra: Dark, vertical and separated lines set against a background of the continuous spectrum of white light.Activity: The number of radioactive disintegrations per unit time.Alpha decay: The spontaneous and random decay of a radioactive nucleus with the emission of an alpha particle.Adiabatic change: The change in pressure, volume and temperature of a system without heat entering or leaving the system.Alpha particle (radiation): A helium nucleus consisting of 2 protons and 2 neutrons. It is emitted from a radioactive nucleus at high speed during an alp