SPM Physics Form 4 and Form 5 Vocabulary

Vocabulary definitions for SPM Physics Form 4 and Form 5, covering Measurement, Force and Motion, Gravitation, Heat, Waves, Light and Optics, Pressure, Electricity, Electromagnetism, Electronics, Radioactivity, and Quantum Physics.

Physical quantity

Quantity that can be measured.

Base quantity

Physical quantity which cannot be derived from another physical quantity.

Derived quantity

Physical quantity derived from base quantity by multiplication or division or both.

Scalar quantities

Physical quantities that have magnitude only

Vector quantities

Physical quantities that have both magnitude and direction.

Linear motion

Motion in a straight line.

Distance

Total length of path travelled

Displacement

Shortest distance between the starting point and the end point in a specific direction.

Speed

Rate of change of distance

Velocity

Rate of change of displacement.

Acceleration

Rate of change of velocity.

Average speed

Rate of change of total distance.

Average velocity

Rate of change of total displacement.

One tick

The time interval between two adjacent dots.

Free fall

Motion of the object is affected only by gravitational force.

Gravitational acceleration

The acceleration of a free falling object caused by gravitational force.

Inertia

Tendency of an object to remain at rest or remain at constant velocity in a straight line

Newton’s First Law

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

Momentum

The product of mass and velocity.

Principle of Conservation of Momentum

The total momentum before collision is equal to the total momentum after collision if no external force is acting on the system

Force

A push or a pull.

Newton’s Second Law of Motion

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

Impulse

Change of momentum

Impulsive force

Rate of change of momentum during a collision

Newton’s Third Law of Motion

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

Mass

The quantity of matter in an object

Weight

The gravitational force acting on an object

Gravitational field strength

Gravitational force acting per unit mass

Gravitational force

The universal force that acts between any two bodies in the universe

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 centres of the two bodies.

Centripetal force

The force that maintains a body in a circular motion and constantly acts towards the centre of the circle.

Kepler’s First Law

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

Kepler’s Second Law

A line that connects a planet to the Sun sweeps out 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 its orbital radius (Law of Periods).

Escape velocity

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

Heat

A form of energy that is transferred between two objects in thermal contact

Temperature

Degree of hotness of an object

Absolute temperature

Temperature measured in Kelvin

Thermal equilibrium

The state where there is zero net heat transfer between two objects in thermal contact that have reached the same final temperature.

Thermometric property

A physical property which changes with temperature. (such as length of column of liquid)

Calibration

A process of making a scale of reading on a thermometer.

Heat capacity

The quantity of heat needed to raise the temperature of the object by $1^\circ\text{C}$.

Specific heat capacity

The quantity of heat needed to raise the temperature of $1\,kg$ mass of the substance by $1^\circ\text{C}$.

Latent heat

The quantity of heat absorbed or released during the change of phase without the change in temperature.

Specific latent heat

The quantity of heat that is absorbed or released during the change of phase of $1\,kg$ of the substance without the change in temperature.

Specific latent heat of fusion

The quantity of heat that is absorbed during melting or released during freezing of $1\,kg$ of the substance without the change in temperature.

Specific latent heat of vaporisation

The quantity of heat that is absorbed during boiling or released during condensation of $1\,kg$ of the substance without the change in temperature.

Kinetic Theory of Matter

The higher the average kinetic energy of molecules, the higher the temperature of the object.

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.

Absolute zero

The lowest possible temperature.

Progressive wave

Waves that propagates through a medium with time

Stationary wave

Waves that do not propagate with time.

Mechanical wave

Waves that require a medium to transfer energy.

Transverse wave

Waves in which the medium particles vibrate in the direction perpendicular to the direction of wave propagation.

Longitudinal wave

Waves in which the medium particles vibrate in the direction parallel to the direction of wave propagation.

Amplitude

Maximum displacement of a particle from its equilibrium position.

Period

The time taken by a particle to make one complete oscillation.

Frequency

Number of complete oscillations made by a particle in one second.

Wavelength

Distance between two consecutive points in phase.

Speed of Wave

Distance travelled per second by a wave profile.

Damping

The decrease in amplitude of an oscillating system due to the loss of energy.

Natural frequency

The frequency of an oscillating system without the action of external forces.

Resonance

The phenomenon where a system oscillates with maximum amplitude due to a periodic force applied at its natural frequency.

Wavefront

A line that joins the points in phase in a wave.

Reflection of waves

The change in direction of wave propagation when the wave strikes an obstacle.

Refraction of waves

The change in direction of wave propagation caused by the change in velocity when the wave propagates from on medium to another.

Diffraction of waves

The spreading of waves when the waves propagate through a slit or side of a barrier.

Interference of waves

Superposition of two or more waves from a coherent source.

Principle of superposition

When two waves overlap, the resultant displacement is the sum of the individual displacements of the two waves.

Coherent source

Sources of waves that have same frequency and constant phase difference.

Constructive Interference

Superposition of two crests or two troughs to produce maximum amplitude.

Destructive Interference

Superposition of a crest and a trough to produce zero combined amplitude.

Electromagnetic waves

Waves that are made up of an electric field and a magnetic field that oscillate perpendicularly to one another.

Refraction of light

The bending of light when it travels though mediums of different optical density due to the change in velocity of light.

Refractive index

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

Critical angle

The incident angle in the optically denser medium when the refracted angle in the optically less dense medium is 90 degrees.

Total internal reflection

Phenomenon where light is totally reflected as it travels from a medium of high to low optical density with the incident angle is larger than the critical angle.

Optical centre

Point at the centre of the lens where light rays passing through are not refracted.

Principal 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 principle axis.

Focal point (Convex Lens)

A point on the principal axis where all light rays parallel to the principal axis converge after passing through the convex lens.

Focal point (Concave Lens)

A point on the principal axis where all light rays parallel to the principal axis appear to diverge after passing through the concave lens.

Object distance

Distance between object and optical centre of a lens.

Image distance

Distance between image and optical centre of a lens.

Focal length

Distance between focal point and optical centre of a lens

Power of lenses

The ability to bend a light ray entering the lens./The reciprocal of the focal length.

Linear magnification

Ratio of image height to the object height.

Real image

Image that can be formed on the screen.

Virtual image

Image that cannot be formed on the screen.

Resultant force

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

Free body diagram

A diagram that shows all the forces acting on that object only.

Resolution of forces

The process of resolving a force into two components.

Equilibrium of Forces

Resultant force acting on an object is zero.

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

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

Elastic limit

The maximum force that can be applied to a spring such that the spring will be able to be restored to its original length when the force is removed.

Spring constant

Ratio of the force applied on a spring to the extension of the spring.

Elastic potential energy

Energy stored in an elastic body when being stretched or compressed.