Key Definitions

• Random errors


  Errors of measurements in which the measured quantities differ from the mean value with different magnitudes and directions
• Systematic errors


  Errors of measurements in which the measured quantities are displaced from the true value by fixed magnitude and in the same direction
• Accuracy


  A measure of how close the results of an experiment agree with the true value
• Precision


  A measure of how close the results of an experiment agree with each other
• Internal energy


  A function of state and the total microscopic kinetic and potential energies of the particles composing the system
• Specific latent heat of fusion, Lf

  The amount of heat required per unit mass to
• Speed


  The rate of change of distance traveled with respect to time
• Velocity


  The rate of change of its displacement with respect to time
• Acceleration


  The rate of change of its velocity with respect to time
• Normal contact force


  A force perpendicular to the surface experienced by a body when it is in physical contact with something else
• Hooke's Law


  Within the limit of proportionality, the extension produced in a material is directly proportional to the load applied
• Principle of moments


  When an object is in equilibrium, the sum of anticlockwise moments about any point equals the sum of clockwise moments about the same point
• Moment of a force

  The product of the force and the perpendicular distance between the axis of rotation and the line of action of the force
• Couple


  A pair of forces, equal in magnitude but opposite in direction, whose lines of motion do not coincide
• Centre of gravity


  The point on an object through which the entire weight of the object may be considered to act
• Stability of an object


  Its ability to return to its original position after it has been displaced from that position
• Pressure


  Force acting per unit area
• Upthrust/buoyancy force


  An upward force on a body produced by the surrounding fluid (i.e., a liquid or a gas) in which it is fully or partially immersed, due to the pressure difference of the fluid between the top and bottom of the object
• Archimedes' Principle


  The upthrust experienced by an object partially or entirely immersed in a fluid is equal to the weight of the fluid displaced by the object
• Newton's first law of motion

  A body will continue in its state of rest or uniform motion in a straight line unless an external resultant force acts on it
• Newton's second law


  The rate of change of momentum of a body is proportional to the resultant force acting on it and the change takes place in the direction of the force
• Newton's third law


  If body A exerts a force on body B, then body B exerts a force of equal magnitude but in the opposite direction on body A
• Principle of conservation of momentum


  The total momentum of a system of objects remains constant provided no resultant external force acts on the system
• Work


  The mechanical transfer of energy to a system or from a system by an external force on it
• Heat


  The non-mechanical transfer of energy from the environment to the system or from the system to the environment because of a temperature difference between the two
• Principle of conservation of energy


  Energy cannot be created nor destroyed in any process
• Gravitational Potential Energy


  The amount of work done in order to raise the body to the height h from a reference level
• Power


  The rate of work done or energy converted with respect to time
• Angular displacement, θ


  The angle subtended at centre of a circle by an arc of equal length to the radius
• Angular velocity, ω


  The rate of change of angular displacement with respect to time
• Period T


  The time taken for the object to make one complete revolution
• Frequency f


  The number of complete revolutions made by the object per unit time
• Displacement


  The distance moved by the particle from its equilibrium position
• Amplitude


  The maximum displacement of the particle from its equilibrium position
• Wavelength


  The distance between 2 successive points on a wave which are in phase with one another
• Period


  The time taken for a particle on the wave to complete one oscillation
• Frequency


  The number of complete oscillations that pass through a given point in 1 second
• Compression

  A region where particles are close to one another (High pressure)
• Rarefaction


  A region where the particles are further apart (Low pressure)
• Phase Difference (φ)


  How much a particle (or wave) is in front or behind another particle (or wave)