Physics IGCSE

Speed

Distance traveled per unit time.

Velocity

Change in displacement per unit time (speed in a given direction).

Acceleration

Rate of change of velocity.

Mass

Property that resists change in motion (inertia) and specifies the amount of matter.

Weight

The force of gravity acting on an object's mass.

Density

Mass per unit volume of a substance.

Force

An action that can change the motion, size, or shape of an object.

Resultant Force

The single overall force remaining when all forces acting on an object are combined.

Vector

A quantity that has both a magnitude and a direction.

Scalar

A quantity that has a magnitude only.

Terminal Velocity

The constant maximum velocity reached by a falling object when its weight equals air resistance.

Moment

The turning effect of a force about a pivot.

Principle of Moments

For an object in equilibrium, the sum of clockwise moments equals the sum of anticlockwise moments.

Limit of Proportionality

The point on a force-extension graph beyond which Hooke's Law no longer applies.

Momentum

The product of an object's mass and its velocity.

Impulse

Force multiplied by the time for which it acts (equals change in momentum).

Principle of Conservation of Momentum

The total momentum before a collision equals the total momentum after a collision in an isolated system.

Work Done

Product of a force and the distance moved in the direction of the force. It is only done when an object moves under the influence of a force.

Power

Rate at which work is done or rate at which energy is transferred.

Efficiency

The percentage of input energy or power that is converted into useful output.

Pressure

Force exerted per unit area.

Distance-Time Graph Gradient

Represents the speed of the object.

Distance-Time Graph Horizontal Line

Represents that the object is stationary.

Velocity-Time Graph Gradient

Represents the acceleration of the object.

Velocity-Time Graph Horizontal Line

Represents that the object is moving with constant speed.

Area Under a Velocity-Time Graph

Represents the total distance traveled by the object.

Condition for Terminal Velocity

Weight equals air resistance, causing zero resultant force and zero acceleration.

Centripetal Force Direction

Acts perpendicular to motion, directed toward the centre of the circular path.

Centripetal Velocity Change

Speed remains constant but velocity changes because the direction of motion constantly changes.

Hooke's Law Graph Linear Region

The straight-line section where force is directly proportional to extension.

Two conditions for equilibrium

The resultant force must be zero, and the net turning moment must be zero.

Elastic Collision Behavior

Objects collide and bounce off each other separately, conserving kinetic energy.

Inelastic Collision Behavior

Objects collide and stick together, losing some kinetic energy to thermal stores.

Law of Conservation of Energy

Energy cannot be created or destroyed, it can only be transferred between stores.

Sankey diagram arrow width

Represents the amount or proportion of energy being transferred.

Gravitational Field Strength (g)

The force per unit mass exerted by a gravitational field (approx 9.8 or 10 N/kg on Earth).

Center of Gravity

The single point on an object through which its entire weight appears to act.

To improve the stability of an object

Lower the center of gravity and widen its base.

depth and density

Pressure in a liquid increases with

Kinetic particle model of matter

Tiny particles that make up matter are always in continuous random motion.

Brownian motion

Random movement of microscopic particles in a fluid due to the collisions by the molecules of the fluid, discovered by randomly moving pollen grains in water.

exerts pressure on it.

The constant collision of air particles on the walls of the container

One degree change on the Kelvin scale

is the same as one degree change on the Celsius scale.

Internal energy

The total energy of all its particles.

Specific heat capacity

The amount of thermal energy required to raise the temperature of a unit mass of a substance by 1°C.

Absolute zero

The lowest possible temperature where particles have zero kinetic energy and stop moving, equal to 0 K or −273 °C.

0°C

The melting point of pure water at standard atmospheric pressure of 1 atmosphere is

100°C

The boiling point of pure water at standard atmospheric pressure of 1 atmosphere is

temperature of liquid, surface area of liquid, and moving air.

Rate of evaporation is affected by

higher temperature to lower temperature until thermal equilibrium is reached.

Thermal energy always flows from a region of

difference in temperature.

Net flow of thermal energy occurs only when there is a

conduction, convection, and radiation.

Heat is transferred through

how quickly thermal energy is transferred from the hotter end to the colder end.

The thermal conductivity of a material is dependent on

lattice vibrations of particles and free electron diffusion.

In metals, thermal energy is transferred through

lattice vibrations

In nonmetals, only __ __ of particles take place.

difference in density.

Convection is in fluids through convection currents due to a

Thermal/infrared radiation

Transfer of thermal energy in the form of invisible waves which can travel through a vacuum.

infrared radiation.

All objects with a temperature above absolute zero emit

color, texture, temperature, area

Factors that affect emission/absorption of thermal radiation: (surface…)

Wave motion

Made up of periodic motion (repeated at regular intervals).

Oscillation/vibration

One complete periodic (swinging from the extreme left to right and back to the starting position) cycle.

Wave

A disturbance that transfers energy, not matter, from one place to another.

Transverse waves

Propagate perpendicular to the direction of the vibration (water, electromagnetic, seismic S-waves, etc).

Longitudinal waves

Propagate parallel to the direction of the vibration (only sound and seismic P-waves).

Amplitude (A, in m)

The maximum displacement of a point from its rest position.

Crest

The highest point of a transverse wave.

Trough

The lowest point of a transverse wave.

Wavelength (λ, in cm or m)

The distance between two successive crests or troughs.

Displacement-distance graph

Describes the displacements of all particles at a particular point in time.

Displacement-time graph

Describes the displacement of one particle over a time interval.

Period (T, in s)

The time taken to produce one complete wave (equivalent to the time taken for the wave to travel through a distance equal to its wavelength).

Frequency (f, in kHz or Hz)

The number of complete waves produced per second (the number of crests/troughs that go past a point per second).

Wave speed (v, in m/s)

The distance travelled by a wave per second.

Wavefront

An imaginary line on a wave that joins all adjacent wave crests (can be straight lines/concentric circles/etc).

Reflection

When waves bounce off the plane surface without changing shape (they hit the barrier at an angle i and get reflected at an angle r, which are equal).

Refraction

When waves pass from one medium to another and change direction/bend (if angle i is zero, r is zero, and it does not occur).

Diffraction

When waves spread out as they encounter gaps and edges (the wavelength does not change).

Diffraction at a gap

When wavelength is longer than _ size, waves spread out more. When wavelength is shorter than _ size, waves spread out less.

Diffraction at an edge

The longer the wavelength, the greater the curvature effect (a greater proportion of the wave will curve around & spread behind the _).

Beam of light

Bundle of light rays and can be parallel, convergent, or divergent rays.

Represent light rays from a distant object

Parallel lines

Represent rays from a nearby object

Divergent lines

Incident ray

The ray that hits the reflecting surface.

Point of incidence

The point at which the incident ray hits the reflecting surface.

Reflected ray

The ray that bounces off the reflecting surface.

Law of reflection

The angle of incidence i is equal to the angle of reflection r.

Normal (line)

The imaginary line perpendicular to the reflecting surface at the point of incidence.

Angle of incidence (i)

The angle between the incident ray and the normal.

Angle of reflection (r)

The angle between the reflected ray and the normal.