Grade 12 Physical Sciences Examination Guidelines 2021

Comprehensive practice flashcards covering key definitions, laws, and principles for Grade 12 Physical Sciences as per the 2021 South African Department of Basic Education Examination Guidelines.

What is the format, duration, and total marks for Physical Sciences Paper 1 (Physics)?

10 multiple-choice questions (20 marks) and structured questions (130 marks), for a total of 150 marks with a duration of 3 hours.

How is Normal Force ($N$) defined?

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.

Define Frictional Force ($f$).

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

What is the difference between static frictional force ($f_s$) and kinetic frictional force ($f_k$)?

Static frictional force opposes the tendency of motion of a stationary object relative to a surface, while kinetic frictional force opposes the motion of a moving object relative to a surface.

State 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.

State Newton's second law of motion in terms of acceleration.

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

State Newton's third law of motion.

When object A exerts a force on object B, object B SIMULTANEOUSLY exerts an oppositely directed force of equal magnitude on object A.

State 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.

How is linear momentum defined?

The product of an object's mass and its velocity, represented by the formula $p = mv$.

State Newton's second law of motion in terms of momentum.

The net (or resultant) force acting on an object is equal to the rate of change of momentum of the object in the direction of the net force ($F_{net} = \frac{\triangle p}{\triangle t}$).

Define Impulse.

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

State the principle of conservation of linear momentum.

The total linear momentum of an isolated system remains constant (is conserved).

What characterizes an isolated system in Physics?

A system on which the net external force is zero.

Define Free Fall.

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

How is the work done on an object by a constant force $F$ defined?

$W = F \triangle x \text{cos}(\theta)$, where $F$ is the magnitude of the force, $\triangle x$ is the magnitude of the displacement, and $\theta$ is the angle between the force and the displacement.

State the work-energy theorem.

The work done on an object by a net force is equal to the change in the object's kinetic energy ($W_{net} = \triangle K = K_f - K_i$).

What is the difference between a conservative and a non-conservative force?

A conservative force (e.g., gravitational force) is one where the work done moving an object between two points is independent of the path taken; a non-conservative force (e.g., friction) depends on the path taken.

State the principle of conservation of mechanical energy.

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

Define 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.

State Coulomb's Law.

The magnitude of the electrostatic force exerted by one point charge ($Q_1$) on another point charge ($Q_2$) is directly proportional to the product of the magnitudes of the charges and inversely proportional to the square of the distance ($r$) between them.

How is the electric field at a point defined?

The electrostatic force experienced per unit positive charge placed at that point ($E = \frac{F}{q}$).

State Ohm's Law.

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

Define the term emf ($\text{ε}$).

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

Define the rms potential difference for an alternating voltage.

The AC potential difference which dissipates/produces the same amount of energy as an equivalent DC potential difference.

Define the Photoelectric Effect.

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

Define Threshold Frequency ($f_o$) and Work Function ($W_o$).

Threshold frequency is the minimum frequency of light needed to emit electrons from a certain metal surface; Work function is the minimum energy that an electron in the metal needs to be emitted.

What is the molar volume of any gas at STP?

$22.4 \text{ dm}^3$ at $0 \text{ }^{\text{o}}\text{C}$ ($273 \text{ K}$) and $1$ atmosphere ($101.3 \text{ kPa}$).

Define Boiling Point.

The temperature at which the vapour pressure of a substance equals atmospheric pressure.

What are structural isomers?

Organic molecules with the same molecular formula, but different structural formulae.

Define Heat of Reaction ($\triangle H$).

The energy absorbed or released in a chemical reaction.

Define Activation Energy.

The minimum energy needed for a reaction to take place.

State Le Chatelier's principle.

When the equilibrium in a closed system is disturbed, the system will re-instate a new equilibrium by favouring the reaction that will oppose the disturbance.

Define an acid and a base according to the Lowry-Brønsted theory.

An acid is a proton ($H^+$ ion) donor; a base is a proton ($H^+$ ion) acceptor.

How is a concentrated acid/base distinguished from a dilute one?

Concentrated acids/bases contain a large amount of acid/base in proportion to the volume of water; dilute ones contain a small amount.

Define Hydrolysis.

The reaction of a salt with water.

Define Oxidation and Reduction in terms of electron transfer.

Oxidation is the loss of electrons; Reduction is the gain of electrons.

What is the function of an Anode and a Cathode?

The anode is the electrode where oxidation takes place; the cathode is the electrode where reduction takes place.