Physics Key terms

This is falsh cards for physical science grade 12 exams. This is meant for SACAI as this will help with navigating their strict marking guides.

Scalar

A physical quantity that has magnitude only.

Vector

A physical quantity that has magnitude and direction.

Resultant

A vector sum of two or more vectors. OR A single vector having the same effect as two or more vectors together.

Equilibrium

is when the forces are balanced and the resultant is zero

Normal force, (F_N)

the force or the component of a force which a surface exerts on an object with which it is in contact, and which is perpendicular to the surface.

Frictional force ,(F_f)

the force that opposes the motion of an object and which acts parallel to the surface.

Static frictional force, (ƒ_S)

the force that opposes the tendency of motion of a stationary object relative to a surface.

Kinetic frictional force, (ƒ_K)

as the force that opposes the motion of a moving object relative to a surface.

Newton's first law of motion

A body will remain in its state of rest or motion at constant velocity unless a non-zero resultant/net force acts on it.

Newton's second law of motion

When a resultant/net force acts on an object, the object will accelerate in the direction of the force at acceleration directly proportional to the force and inversely proportional to the mass of the object.

Newton's third law of motion

When one body exerts a force on a second body, the second body exerts a force of equal magnitude in the opposite direction on the first body.

Newton's Law of Universal Gravitation

Each body in the universe attracts every other body with a force that is directly proportional to the product of their masses and inversely proportional to the square of the distance between their centres.

Momentum

the product of an object's mass and its velocity

Newton's second law of motion in terms of momentum

The resultant/net force acting on an object is equal to the rate of change of momentum of the object in the direction of the resultant/net force.

Impulse

the product of the resultant/net force acting on an object and the time the resultant/net force acts on the object.

Closed/an isolated system (in Physics)

a system on which the resultant/net external force is zero. A closed/an isolated system excludes external forces that originate outside the colliding bodies, e.g. friction. Only internal forces.

The principle of conservation of linear momentum

The total linear momentum of a closed system remains constant (is conserved)

A projectile

an object upon which the only force acting is the force of gravity

Free fall

motion during which the only force acting on an object is the gravitational force.

Work Done

is the energy transferred to or from an object through the application of force along a displacement

Work-energy theorem

The net/total work done on an object is equal to the change in the object's kinetic energy OR the work done on an object by a resultant/net force is equal to the change in the object's kinetic energy.

A conservative force

a force for which the work done in moving an object between two points is independent of the path taken

A non-conservative force

a force for which the work done in moving an object between two points depends on the path taken

Principle of conservation of mechanical energy

The total mechanical energy (sum of gravitational potential energy and kinetic energy) in an isolated system remains constant.

Power

the rate at which work is done or energy is expended.

The Doppler effect

the change in frequency (or pitch) of the sound detected by a listener because the sound source and the listener have different velocities relative to the medium of sound propagation

Coulomb's law

The magnitude of the electrostatic force exerted by one point charge (Q1) on another point charge (Q2) is directly proportional to the product of the magnitudes of the charges and inversely proportional to the square of the distance (r) between them

Electric field

a region of space in which an electric charge experiences a force. The direction of the electric field at a point is the direction that a positive test charge would move if placed at that point.

Electric field at a point

The electric field at a point is the electrostatic force experienced per unit positive charge placed at that point

Ohm's law

The potential difference across a conductor is directly proportional to the current in the conductor at constant temperature

Emf

the maximum energy provided by a battery per unit charge passing through it.

Rms for an alternating voltage or an alternating current

The rms value of AC is the DC potential difference/current which dissipates the same amount of energy as AC.

The photoelectric effect

the process whereby electrons are ejected from a metal surface when light of suitable frequency is incident on that surface.

Threshold frequency, (ƒ_o)

the minimum frequency of light needed to emit electrons from a certain metal surface

Work function, (W_o)

the minimum energy that an electron in the metal needs to be emitted from the metal surface