AS LEVEL DEFINITIONS 1. Base unit - stand alone units from which other units are derived 2. Derived unit - products or quotients of the base units 3. Scalar quantity - quantity that has magnitude only 4. Vector quantity - quantity that has magnitude and direction 5. Systematic error - error that causes the readings to have a constant deviation from either side of the actual reading. 6. Random error - error that causes the readings to scatter around the mean value 7. Distance is the total path traveled. 8. Displacement is the shortest distance between a start point and an end point. 9. Speed is total distance traveled divided by time taken 10.Velocity - rate of change of displacement 11. Acceleration - rate of change of velocity 12.Mass - property of a body resisting changes in motion 13.Mass - quantity of matter in a body 14.Newton's 1st Law - A body continues at rest or constant velocity unless acted upon by a resultant force 15.Newton's 2nd Law - The rate of change of momentum is proportional to the resultant force and it occurs in the same direction as the force. 16.Newton's 3rd Law - If body A exerts a force on body B, body B exerts a force of equal magnitude on body A but opposite in direction. 17.Momentum - product of mass and velocity 18.Principle of conservation of momentum - total momentum of an isolated system of bodies is constant 19.Force - rate of change of momentum 20.Conditions for equilibrium - zero resultant force in any direction, zero resultant moment about any point 21.Centre of gravity - The point on a body where weight of the object is considered to act on 22.Moment - force x perpendicular distance from the point of moment to the line of action of the force 23.Couple - a pair of parallel forces that are equal in magnitude but opposite in direction, and they are not in line. 24.Torque - product of one of the force of a couple and the perpendicular distance between the pair of forces 25.Work done - force x distance moved in the direction of the force 26.Energy - the ability to do work 27.Power the rate of work done 28.Kinetic energy - energy an object has due to its motion 29.Gravitational potential energy - energy a mass stored due to its position in a gravitational field 30.Elastic potential energy - energy store in a body due to its deformation 31.Efficiency - useful output power divided by input power 32.Density - mass divided by volume 33.Pressure - force x area normal to the force 34.Hooke's Law - extension is directly proportional to the force, provided that the proportionality limit is not exceeded 35.Stress - force per unit cross-sectional area 36.Strain - change in length per unit original length 37.Young modulus - stress divided by strain 38.Amplitude - maximum displacement from equilibrium position 39.Wavelength - minimum distance between two points having the same displacement and moving in the same direction 40.Wavelength - distance between two adjacent wavefronts 41.Wavelength - distance moved by a wavefront during one period 42.Frequency - number of oscillations per unit time 43.Frequency - number of wavefronts passing through a point per unit time 44.Period - time taken by a particle to complete one oscillation 45.Intensity - rate of energy transfer per unit area 46.Transverse wave - a wave on which oscillations of particles are perpendicular to the direction of propagation of the wave 47.Longitudinal wave - a wave on which oscillations of particles are parallel to the direction of propagation of the wave 48.Diffraction - spreading of a wave into its geometrical shadow when it passes through a slit 49.Principle of superposition - when two or more waves meet at a point, the resultant displacement is equal to the sum of the individual displacement of each wave 50.Coherent sources - sources of wave with constant phase difference 51.Electric field - a region in space where a charge experiences an electric force 52.Electric field strength - force per unit positive charge 53.Charge - product of current and time 54.coulomb - ampere second 55.volt - joule / coulomb 56.ohm - volt / ampere 57.Potential difference - energy per unit charge converted from electrical energy to other forms of energy 58.e.m.f - energy per unit charge converted from other forms of energy to electrical energy 59.Resistance - ratio of p.d. to current 60.Kirchhoff's 1st Law - Algebraic sum of the currents at a junction is zero 61.Kirchhoff's 1st Law - sum of currents into a junction = sum of currents out of the junction 62.Kirchhoff's 2nd Law - In a closed loop of circuit, the algebraic sum of the potential difference is equal to the algebraic sum of the e.m.f 63.Isotopes - nuclei of a particular element with the same number of protons, but different number of neutrons
