Physics Definitions & Terms F4F5

Physics F4F5 Definitions & Terms

• Physical quantity: A measurable property of a physical system.
• Base quantity: A fundamental quantity that cannot be expressed in terms of other quantities.
• Derived quantity: A quantity that can be expressed as a combination of base quantities.
• Scalar quantity: A physical quantity with magnitude only.
• Vector quantity: A physical quantity with both magnitude and direction.
• Linear motion: Motion in a straight line.
• Speed: Rate of change of distance.
• Velocity: Rate of change of displacement.
• Acceleration: Rate of change of velocity.
• Free fall motion: Motion of an object falling under the influence of gravity only.
• Inertia: Tendency of an object to resist changes in its state of motion.
• Newton's first law of motion: An object at rest stays at rest and an object in motion stays in motion with the same speed and in the same direction unless acted upon by an unbalanced force.
• Momentum: Product of mass and velocity.
• Force: Action of pushing or pulling that can change the size and direction of motion.
• Newton's second law of motion: Rate of change of momentum is directly proportional to the net force acting on the object.
• Impulse: Change of momentum in a collision or impact over a short period.
• Impulsive force: Rate of change of momentum during a collision.
• Newton's third law of motion: For every action, there is an equal and opposite reaction.
• Weight: Gravitational force acting on an object.
• Newton's universal law of gravitation: Attractive force between two bodies is directly proportional to the product of their masses and inversely proportional to the square of the distance between their centres.
• Centripetal force: Force acting on an object moving in a circular path and directed towards the centre.
• Kepler's first law: Planets move in elliptical orbits with the Sun at one focus.
• Kepler's second law: A line joining a planet and the Sun sweeps out equal areas during equal intervals of time.
• Kepler's third law: Squares of the orbital periods of planets are directly proportional to the cubes of the semi-major axes of their orbits.
• Orbital radius: Average distance between a planet and the Sun.
• Escape velocity: Minimum velocity needed for an object to escape a planet's gravitational pull.
• Temperature: Measure of the degree of hotness of an object.
• Heat: Amount of thermal energy transferred between objects.
• Thermal equilibrium: Condition where there is no net heat transfer between objects.
• Heat capacity: Quantity of heat needed to raise the temperature of an object by 1°C.

Physics F4F5 Concepts (Page 2)

• Specific heat capacity: Amount of heat needed to raise the temperature of 1 kg of a substance by 1°C.
• Latent heat: Heat absorbed or released during a phase change without a change in temperature.
• Specific latent heat of fusion: Amount of heat needed to change 1 kg of a substance from solid to liquid (or vice versa) without a change in temperature.
• Specific latent heat of vaporisation: Amount of heat needed to change 1 kg of a substance from liquid to gas (or vice versa) without a change in temperature.
• Boyle's law: Pressure of a gas is inversely proportional to its volume at a constant temperature.
• Charles' law: Volume of a gas is directly proportional to its absolute temperature at a constant pressure.
• Gay-Lussac's law: Pressure of a gas is directly proportional to its absolute temperature at a constant volume.
• Oscillation/Vibration: Repetitive motion about an equilibrium position.

Physics F4F5 Concepts (Page 3)

• Amplitude: Maximum displacement from equilibrium position.
• Transverse wave: Wave where the oscillations are perpendicular to the direction of wave propagation.
• Longitudinal wave: Wave where the oscillations are parallel to the direction of propagation.
• Period: Time taken for one complete oscillation/cycle.
• Frequency: Number of oscillations/cycles per second.
• Wavelength: Distance between two adjacent points in phase.
• Wave speed: Distance a wave travels per unit time.
• External damping: Loss of energy due to friction or air resistance.
• Internal damping: Loss of energy due to stretching and compression of vibrating particles.
• Damping: Reduction in amplitude of oscillation over time.
• Resonance: Condition where a periodic force applied to an oscillating system amplifies the amplitude of oscillations.
• Wavefront: Lines joining all points on a wave that are in the same phase.
• Refraction: Change in direction of a wave as it travels from one medium to another.
• Diffraction: Spreading out of waves as they pass through an opening or boundary.
• Interference: Superposition of two or more waves.
• Constructive Interference: Occurs when two crests or troughs are in superposition and result in a maximum amplitude.
• Destructive Interference: Occurs when a crest and a trough are in superposition and result in a zero amplitude.
• Electromagnetic spectrum: Range of all types of electromagnetic waves.
• Electromagnetic wave: Waves consisting of oscillating electric and magnetic fields.
• Refraction of light: change in the direction of light when traveling from one medium to another.
• Refractive index: Ratio of the speed of light in a vacuum to the speed of light in a medium.
• Snell's law: Relationship between angles of incidence and refraction of light at the boundary between two media.
• Total internal reflection: Incident angle of light is more than the critical angle, light reflects internally.
• Critical angle: Angle of incidence at which the refracted ray travels along the boundary between the two media.

Physics F4F5 Optics (Page 3)

• Optical center: Point on a lens through which light passes without deviation.
• Principle axis: Line passing through the optical centre and perpendicular to the principal plane of a lens.
• Focal point: Point where light rays converge after passing through a lens
• Object distance: Distance from the optical centre to an object.
• Image distance: Distance from the optical centre to an image.
• Focal length: Distance between the focal point and the optical centre of a lens.
• Linear magnification: ratio of image height to object height.
• Principal axis: Line passing through the center of curvature and pole of the spherical mirror.
• Center of curvature (C): Center of the sphere from which the spherical mirror is a part.
• Radius of curvature (r): Radius of that sphere.
• Focal point (F): Point on the principle axis where parallel rays converge or appear to diverge after reflection from a mirror.
• Object distance (u): Distance between the object and pole of the mirror.
• Image distance (v): Distance between the image and pole of the mirror.
• Focal length (f): Distance between the focal point and the pole of the mirror.