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

Length of route covered by an object.

Displacement

Shortest distance between the initial position and the final position in a specific direction.

Speed

Rate of change of distance travelled.

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, if moving, to continue its motion in a straight line at uniform velocity.

Newton’s First Law

An object will remain at rest or move 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 it.

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

A change in momentum

Impulsive force

The 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

Gravitational pull acting on an object towards the centre of Earth.

Gravitational field strength

Force acting per unit mass caused by gravitational pull.

Gravitational force

Force of attraction 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

For a body in circular motion, 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 equal areas in equal times (Law of Areas).

Kepler’s Third Law

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

Escape velocity

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.

Temperature

Degree of hotness of a substance.

Thermal equilibrium

Net heat transfer between the two objects in thermal contact becomes zero.

Thermometric property

A physical property which can be measured 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

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

Specific latent heat

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

Specific latent heat of fusion

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

Specific latent heat of vaporisation

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

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

Wave profile which propagates with time along the direction of propagation of the wave.

Stationary wave

Wave profile which does not propagate with time.

Transverse wave

Particles of the medium vibrate in the direction perpendicular to the direction of propagation of the wave.

Longitudinal wave

Particles of the medium vibrate in the direction parallel to the direction of propagation of the wave.

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.

Wave speed

Distance travelled per second by a wave profile.

Damping

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

Natural frequency

Frequency of a system which oscillates freely without the action of external forces.

Resonance

When an oscillating system driven at its natural frequency by a periodic force.

Wavefront

An imaginary line which the vibration of every point on it are in phase and at the same distance from the source of a wave.

Refraction of waves

Bending of waves when the waves propagate from one medium to another due to the change in the velocity.

Diffraction of waves

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 of waves.

Principle of superposition

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

Coherent

Waves that have same frequency and constant phase difference.

Real depth

Distance between an object in an optical medium and the surface of the optical medium facing the observer.

Apparent depth

Distance between the image of an object in an optical medium and the surface of the optical medium facing the observer.

Electromagnetic waves

Propagating waves with electric field and magnetic field oscillate perpendicular to each other.

Refraction of light

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

Refractive index

Ratio of speed of light in vacuum to the speed of light in medium.

Critical angle

Angle of incidence in the medium of high optical density when the angle of refraction in the medium of lower optical density is $900$ .

Total internal reflection

Complete reflection of light at the boundary of two medium where the angle of incident exceeds the critical angle of the medium.

Focal length

Distance between focal point and optical centre of a lens

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.

Resolution of forces

The process of resolving a force into two components.

Forces in equilibrium

The forces acting on an object produce a zero resultant 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

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.

Pressure

Force per unit area.

Atmospheric pressure

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

Pascal's principle

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

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 is partially or fully immersed in a fluid will experience a buoyant force equal to the weight of fluid displaced.

Bernoulli's principle

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

Electric field

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

Electric field strength

The electric force acting on a unit positive charge placed at the point.

Current

Rate of flow of charge.

Potential difference

Work done in moving one coulomb of charge from one point to another.

Resistance

Potential difference per unit current.

Resistivity

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

Electromotive force

Energy transferred or work done by an electrical source to move one coulomb of charge in a complete circuit.

Internal resistance

Resistance caused by electrolyte in the dry cell.

240 V, 32 W

$32\,J$ of energy is consumed in one second when connected to $240\,V$ power supply.