Physics Form 4 and 5 Definitions, Terms, and equations and laws

Flashcards based on Physics Form 4 and Form 5 terms, laws, and definitions.

Physical quantity

A quantity that can be measured.

Base quantity

A physical quantity that cannot be derived from another physical quantity.

Derived quantity

A quantity which can be obtained by combination of base quantities by means of multiplication, division or both.

Scalar quantity

Physical quantities that have magnitude only.

Vector quantity

Physical quantities that have both magnitude and direction.

Linear motion

Motion in a straight line.

Speed, v

Rate of change of distance.

Velocity, v

Rate of change of displacement.

Acceleration, a

Rate of change of velocity.

Free fall motion

A situation where an object falls down due to gravitational force only.

Inertia

Tendency of an object to remain at rest or to continue its uniform motion in a straight line at uniform velocity.

Newton’s first law of motion

An object will remain at rest or move at uniform velocity unless acted upon by an external force.

Momentum, p

A product of mass multiplied by velocity.

Force, F

The action of pushing or pulling to change the size and direction of motion of an object.

Newton’s second law of motion

Rate of change of momentum is directly proportional to the force and acts in the direction of the applied force.

Impulse, J

Change of momentum.

Impulsive Force, F

Rate of change of momentum in a collision or impact in a short period of time.

Newton’s third law of motion

For every action there is a reaction of equal magnitude but in the opposite direction.

Weight, W

A gravitational force acting on an object.

Newton’s universal law of gravitation

The gravitational force between two bodies is directly proportional to the product of the masses of both bodies and inversely proportional to the square of the distance between the centers of the two bodies.

Centripetal force

A force acts on the body in a direction towards the centre of the circle.

Kepler’s first law

All planets move in elliptical orbits with the Sun at one focus (Law of Orbits).

Kepler’s second law

A line that connects a planet to the Sun sweeps out the equal areas in equal times (Law of Areas).

Kepler’s third law

The square of the orbital period of any planet is directly proportional to the cube of the radius of its orbit (Law of Periods).

Orbital radius

Average value of the distance between the planet and the Sun.

Escape velocity, v

Minimum velocity needed by an object on the surface of the Earth to overcome the gravitational force and escape to outer space.

Temperature, T

Measure of the degree of hotness of an object.

Heat, Q

The amount of thermal energy that can be transferred from one object to another.

Thermal equilibrium

A condition where net heat transfer between two objects becomes zero.

Heat capacity, C

Quantity of heat needed to raise temperature of the object by 1°C.

Specific heat capacity, c

Quantity of heat needed to raise the temperature of 1kg mass of the substance by 1°C.

Latent heat

Heat that is absorbed during melting and boiling without change in temperature.

Specific latent heat, l

The quantity of heat that is absorbed or released during a change of phase of 1kg of the substance without any change in its temperature.

Specific latent heat of fusion, lf

The quantity of heat that is absorbed during melting or the quantity of heat released during freezing of 1kg of the substance without any change in temperature (solid-liquid | liquid-solid).

Specific latent heat of vaporisation, lv

The quantity of heat that is absorbed during boiling or the quantity of heat released during condensation of 1kg of the substance without any change in temperature (liquid-gas | gas-liquid).

Boyle’s law

Pressure is inversely proportional to volume for a fixed mass of gas at constant temperature.

Charles’ law

Volume is directly proportional to absolute temperature for a fixed mass of gas at constant pressure.

Gay-Lussac’s law

Pressure is directly proportional to absolute temperature of a fixed mass of gas at constant volume.

Oscillation, vibration

Repetitive motions about an equilibrium position in a closed path.

Amplitude, A

Maximum displacement from its equilibrium position.

Transverse wave

A wave which the vibration of particles in the medium is perpendicular to the direction of propagation of the wave.

Longitudinal wave

A wave which the vibration of particles in the medium is parallel to the direction of the wave.

Period, T

The time taken by a particle to make one complete oscillation or by a source to produce one complete cycle of wave.

Frequency, f

Number of complete oscillations made by a particle or number of cycles of wave produced by a source in one second.

Wavelength, λ

Distance between two consecutive points in phase.

Wave speed, v

Distance travelled per second by a wave profile.

External damping

Oscillating system loses energy to overcome friction or air resistance.

Internal damping

Oscillating system loses energy because of the stretching and compression of the vibrating particles in the system.

Damping

Reduction in amplitude in an oscillating system due to loss of energy.

Resonance

When a periodic force is applied to an oscillating system at its natural frequency.

Wavefront

Lines joining all the points of the same phase.

Refraction of waves

The change in direction of propagation of waves caused by the change in the velocity of waves when the waves propagate from one medium to another.

Diffraction of waves

The spreading of waves when the waves pass through a gap or round a barrier.

Interference of waves

The superposition of two or more waves from a coherent source of waves.

Constructive Interference

Occurs when two crests or troughs are in superposition to produce maximum amplitude.

Destructive Interference

Occurs when a crest and a trough are in superposition to produce zero combined amplitude.

Electromagnetic spectrum

Seven types of electromagnetic waves that forms a continuous spectrum.

Electromagnetic wave

Produced when electric and magnetic field vibrate at right angle to each other.

Refraction of light

A phenomenon when light changes direction when it travels from one medium to another medium of different densities.

Refractive index, n

The ratio of speed of light in vacuum to the speed of light in medium.

Snell’s Law

When light travels from one medium to another medium, the incident ray, the refracted ray and the normal meet at one point and are in the same plane.

Total internal reflection

When light travels from a medium with high optical density to a medium of low optical density.

Critical angle, c

Incident angle when refracted angle equal to 90°.

Formation of rainbow

Caused by refraction, dispersion and total internal reflection when light passes through water droplets in air.

Optical centre, O

Points at the centre of the lens.

Principle axis

Straight line through the optical centre of a lens and the centre of curvature of both surfaces of the lens.

Axis of lens

Straight line through the optical centre and perpendicular to the principal axis.

Focal point, F

Point located at the principle axis of a lens.

Object distance, u

Distance between object and optical centre of a lens.

Image distance, v

Distance between image and optical centre of a lens.

Focal length, f

Distance between focal point, F and optical centre, O of a lens.

Linear magnification, m

Ratio of image height to object height = ratio of image distance to object distance.

Principal axis

Straight line passing through the centre of curvature, C and pole of the spherical mirror, P.

Centre or curvature, C

Centre of sphere which produces a concave or convex mirror.

Radius of curvature of mirror, r

Distance between the pole of spherical mirror,P and the centre of curvature, C.

Focal point, F

A point on the principal axis of the spherical mirror.

Object distance, u

Distance between object and the pole of spherical mirror, P.

Image distance, v

Distance between image and the pole of spherical mirror, P.

Focal length, f

Distance between focal point, F and the pole of spherical mirror, P.

Resultant force

The single force that represents the vector sum of two or more forces acting on an object.

Resolution of forces

Process of resolving a force into two components.

Equilibrium of forces

Forces acting on an object produce a zero resulting force.

Elasticity

The property of material that enables an object to return to its original shape and size after the force applied on it is removed.

Hooke’s law

Extension of a spring is directly proportional to the force applied on the spring provided the elastic limit of the spring is not exceeded.

Pressure

Force per unit area.

Atmospheric pressure

Pressure due to the weight of the layer of air acting on the surface of the earth.

Gas pressure

The force per unit area exerted by the gas molecules as they collide with the wall of the container.

Pascal’s Principle

Pressure applied on an enclosed fluid is transmitted uniformly in all direction in the fluid.

Hydraulic system

A system that uses a liquid to transmit pressure.

Buoyant force

Force acting upwards on an object immersed in a liquid when there is pressure difference between the lower surface and upper surface of the object.

Archimedes’ principle

An object which partially or fully immersed in a fluid will experience a buoyant force equal to the weight of fluid displace.

Bernoulli’s principle

When the velocity of a fluid increases, the pressure in the fluid decreases and vice versa.

Electric field

Region around a charged particle where any electric charge in the region will experience an electric force.

Electric field strength, E

Electric force acting on a unit positive charge placed at a point.

Current, I

Rate of flow of charge, Q in a conductor.

Potential difference, V

The work done, W in moving one coulomb of charge, Q from one point to another.

Ohm’s law

The electric current, I flowing through a conductor is directly proportional to the potential difference across it if the temperature and other physical conditions are constant.

Ohmic conductors

Conductors that obey Ohm’s law.

Resistance, R

Ratio of the potential difference across the conductor to the electric current flowing through it.

Resistivity of a conductor, p

A measure of a conductor’s ability to oppose the flow of electric current.