physics

Precision of an instrument

The smallest unit that the instrument can measure.

Precision of experimental results

A measure of how close the experimental results are to each other.

Accuracy

A measure of how close the experimental result is to the true or accepted value.

Scalar

A physical quantity which has magnitude only.

Vector

A physical quantity which has both magnitude and direction.

Distance

The total length travelled by a body regardless of the direction of motion.

Displacement

The distance measured in a straight line in a specified direction.

Speed

The distance traveled per unit time.

Velocity

The rate of change of displacement.

Acceleration

The rate of change of velocity.

Mass

The amount of matter in a body.

Weight

The force of gravity acting on a body.

Gravitational field

A region in which a mass experiences a force due to gravitational attraction.

Hooke’s Law

States that within the limit of proportionality, the extension or compression produced is directly proportional to the elastic force.

Inertia

The resistance of a body to change in its state of rest or motion.

Newton’s 1st Law of Motion

A body will remain in its state of rest or uniform motion unless acted upon by a resultant force.

Newton’s 2nd Law of Motion

The resultant force acting on an object of constant mass is the product of the mass and acceleration of the object.

Newton’s 3rd Law of Motion

If body A exerts a force on body B, then body B exerts an equal and opposite force on body A.

Centre of gravity

The point through which the entire weight of a body appears to act for any orientation of the object.

Moment of a force

The product of the force and the perpendicular distance between the axis of rotation and the line of action of the force.

Torque of a couple

The product of one of the forces and the perpendicular distance between their lines of action.

Principle of Moments

For an object to be in rotational equilibrium, the sum of clockwise moments must equal the sum of anti-clockwise moments.

Translational equilibrium

A body is in translational equilibrium when the resultant force on the body is zero.

Rotational equilibrium

A body is in rotational equilibrium when the resultant moment on the body about every axis is zero.

Density

The mass per unit volume of a substance.

Pressure

The amount of force acting perpendicularly on a unit area.

Work done

The product of a force on a body and its displacement in the direction of the force.

Conservation of energy

Energy cannot be created or destroyed, only converted from one form to another.

Power

The rate of work done or rate of energy conversion.

Refractive index

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

Focal length

The distance between the optical centre and the focal point.

Critical angle

The angle of incidence in the optically denser medium for which the angle of refraction is 90° in the optically less dense medium.

Total internal reflection

The complete reflection of a light ray inside an optically denser medium at its boundary with an optically less dense medium.

Wave

A propagation of a disturbance that carries energy from one point in space to another without transferring matter.

Wave speed

The distance travelled by a wave per second.

Amplitude

The magnitude of maximum displacement of a particle from its equilibrium position.

Frequency

The number of complete waves produced per second.

Period

The time for a particle in the wave to complete one cycle of vibration.

Wavelength

The shortest distance between two points vibrating in phase.

Wavefront

An imaginary line or surface that joins points of a wave that are in phase.

Transverse waves

Waves in which the displacement of the particles is perpendicular to the direction of energy transfer.

Longitudinal waves

Waves in which the displacement of the particles is parallel to the direction of energy transfer.

Ultrasound

Sound with frequencies above the upper hearing limit of the human range of audibility.

Electrostatic charges

Positive and negative charges measured in Coulombs.

Law of electrostatics

Like charges repel and unlike charges attract.

Electric field

A region in which an electric charge experiences an electric force.

Electrical conductors

Materials that allow the flow of electric charge.

Electrical insulators

Materials that do not allow the flow of electric charge.

Electrostatic charging by rubbing

Involves the transfer of electrons between insulators.

Electrostatic charging by induction

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