O Level Physics Definitions

T erm De fi nition Measurement A physical quantity that has magnitude but not direction E.g. Mass, Distance, Speed, Energy A physical quantity that has both magnitude and direction E.g. Force, Displacement, Velocity, Acceleration Scalar Quantity Vector Quantity Kinematics Speed Velocity Acceleration Dynamics Newton's 1st Law of Motion Rate of change of distance Rate of change of displacement Rate of change of velocity An object will continue in its state of rest or uniform motion unless a resultant force acts on it When a resultant force acts on an object of constant mass, the object will accelerate and move in the direction of the resultant force. The product of the mass and acceleration of the object is equal to the resultant force Newton's 2nd Law of Motion Mass, Weight & Density Mass Weight Inertia Gravitational Field Amount of matter or substance in a body Amount of gravitational force acting on a body Reluctance of a body to change its state of rest or moticn Region in which a mass experiences a force due to gravitational attraction Gravitational force per unit mass at a point. Mass per unit volume Gravitational Field Strength Density Turning Effect of Forces Moment of a Force The product of the force and the perpendicular distance from the pivot to the line of action of the force When a body is in equilibrium, the sum of clockwise moments about a pivot is equal to the sum of anticlockwise moments about the same pivot The imaginary point through which the entire weight of an object appears to act for any orientation The ability of an object to return to its original position after it has been tilted slightly Principle of Moments Centre of gravity Stability Pressure Pressure Energy, Work & Power Principle Force exerted/acting per unit area Energy can neither be created nor destroyed. It can only be converted from one form to another or transferred from one body to another, but the total amount of energy remains constant of Conservation of Energy

T erm De fi nition The product of the force on a body and the distance moved by the body in the direction of the force Rate of work done Work Done Power Kinetic Model of Matter The continuous and random motion of smoke particles in air (or pollen grains in water) due to uneven bombardment by air molecules (or water molecules) Brownian Motion Transfer of Thermal Energy Thermal Equilibrium Conduction No net gain or loss of thermal energy between two bodies it contact Process of thermal energy transfer without any fl ow of th material medium (through molecular vibrations) Process of thermal energy transfer by means of bulk monent of the fl uid The continual emission of infrared waves from the surface ofa body, transmitted without the aid of a medium Convection Radiation T emperature Substance which have physical properties that vary continuously with temperature E.g. Resistance, EME, Pressure Points that are of standard degrees of hotness or coldness which are easily obtainable and reproducible T emperature of pure melting ice at one atmospheric pressure T emperature of steam from boiling water at one atmospheric pressure Thermometric Substance Fixed Points lce Point Steam Point Thermal Properties of Matter Internal Energy Heat Capacity Speci fi c Heat Capacity Melting/Solidi fi cation Boiling/Condensation The sum of the energy due to the vibration of the particles (KE) and the stretching and compressing of intermolecular bonds (PE) The amount of thermal energy required to raise the temperature of a substance by unit temperature (1K). The amount of thermal energy required per unit mass (1 kg) to raise the temperature of a substance by unit temperature (1K). The change of state of a substance from solid to liquid (or vice-versa) without a change in temperature The change of state of a substance from liquid to vapour (or vice- versa) without a change in temperature The amount of thermal energy absorbed or released during a change of state without a change in temperature The amount of thermal energy per unit mass (1 kg) required to change a substance from solid to liquid, or vice-versa, without any change in temperature Latent Heat Speci fi c Latent Heat of Fusion

T erm De fi nition Speci fi c Vaporisation The amount of thermal energy required per unit mass (1 kg) to change a substance from liquid to vapour, or vice-versa, without any change in temperature Latent Heat of General Wave Properties The direction in which energy is propagated by the wave Waves in which the direction of the vibration of the particles is perpendicular to the direction of wave motion Waves in which the direction of the vibratiorn of the particles is parallel to the direction of wave motion Points having the direction of motion, speed and displacerment from the rest position The highest point of a transverse wave The lowest point of a transverse wave Maximum displacement from the rest position The time taken for one point on a wave to compiete a full oscillation The number of complete oscillations by one point on a wave per second Distance travelled by the wave in a time of one period Any one of the following: (i) The distance between any two adjacent points that are in phase (ii) The distance between any two adjacent crests or troughs An imaginary line on a wave that joins all points that are in the same phase Wave Motion Transverse Waves Longitudinal Waves In-Phase Crest Trough Amplitude Period Frequency Wavelength Wavefront Light Point of Incidence Normal Angle of Incidence Angle of Re fl ection *First Law of Re fl ection *Second Law of Re fl ection Angle of Refraction Refractive Index The point on a surface where the incident ray hits The perpendicular line to a surface at the point of incidence The angle between the incident ray and the normal The angle between the re fl ected ray and the normal The incident ray, re fl ected ray and the normal to the re fl ecting surface all lie in the same plane The angle of incidence is equal to the angle of re fl ection The angle between the refracted ray and the normal The ratio between the speed of light in vacuum and the speed of light in a medium The angle of incidence in the optically denser medium for which the angle of refraction in the optically less dense medium is 90° The phenomenon in which an incident light ray travelling from an optically denser to less dense medium is fully re fl ected back at the boundary between the two optical media Critical Angle To t a l Internal Re fl ection

T erm De fi nition The point at which all rays parallel to the principal axis converge to after refraction by a lens Focal Point Focal Length Sound The distance between the optical centre and the focal point Regions where the air pressure is slightly higher than the surrounding air pressure Regions where the air pressure is slightly lower than the surrounding air pressure The range of frequencies which a person can hear (typica!iy from 20 Hz to 20 kHz) Sound with frequencies above the upper limit of the huma range of audibility, which is typically around 20 kHz Compression Rarefaction *Range of Audibility Ultrasound Static Electricity Electric Field Region in which an electric charge experiences an electric 'ce De fi ned as the direction of the electric force acting on a srriai positive test charge Force per unit charge on a positive test charge at that point. Direction of Field Lines Electric Field Strength Current of Electricity Current Convention Current Flow Rate of fl ow of electric charge Positive charges fl owing from a positively charged ernd to a negatively charged end Electrons fl owing from a negatively charged end to a positively charged end Work done by a source in driving a unit charge around a complete circuit Work done in driving a unit charge through the component Electron Flow Electromotive Force Potential Difference (across a component) The ratio of the p.d. across a conductor and the current fl owing through it The current passing through a metallic conductor is directly proportional to the potential di