§-Unit

Unit 3: Gravity and electromagnetism

8 dot points, in syllabus order. Each dot point has a focused answer, with exam-style questions and worked answers where available.

Topic 1: Gravity and motion

Apply Newton's law of universal gravitation F = G m1 m2 / r^2 and the gravitational field strength g = G M / r^2 to calculate gravitational force, field strength and acceleration at points in a radial gravitational field

Newton's law of universal gravitation. The inverse-square law, gravitational field strength as force per unit mass, the distinction between G and g, and worked altitude examples of the kind QCAA uses in IA1 stimulus and EA Paper 2.

9 min read →

Solve problems involving projectile motion by resolving the motion into independent horizontal and vertical components, assuming constant downward acceleration due to gravity and negligible air resistance

Projectile motion. Resolves initial velocity into components, applies the constant-acceleration equations to each axis independently, and works the level-ground range and cliff-drop standards QCAA uses in IA1 stimulus and EA Paper 2.

10 min read →

Apply the relationships for orbital motion of satellites and planets, including Kepler's third law T^2 / r^3 = 4 pi^2 / (G M), orbital speed v = sqrt(G M / r), and the energy of an orbit (kinetic, gravitational potential and total)

Orbital motion. Derives orbital speed from setting gravitational force equal to centripetal force, applies Kepler's third law to satellites and planets, and works the kinetic and gravitational potential energies of a circular orbit with the standard QCAA geostationary-satellite example.

11 min read →

Apply the relationships for uniform circular motion, including centripetal acceleration a = v^2/r, centripetal force F = m v^2 / r, period T = 2 pi r / v, and the geometry of banked curves and conical pendulums

Uniform circular motion. Defines centripetal acceleration, identifies the real forces that supply centripetal force in common contexts (string tension, friction, normal-force component, gravity), and works the banked curve and conical pendulum geometries that QCAA expects in IA1 and IA2.

11 min read →

Topic 2: Electromagnetism

Apply Faraday's law of electromagnetic induction (induced EMF = - N dPhi/dt) and Lenz's law to determine the magnitude and direction of induced EMF, including motional EMF in a moving conductor and the induced current in a circuit

Electromagnetic induction. Faraday's law for the induced EMF in a coil, Lenz's law for the direction, the motional-EMF special case for a sliding rod, the energy-conservation argument behind the minus sign, and the standard worked examples QCAA uses in IA1 stimulus and IA2 design.

12 min read →

Apply the relationships for the magnetic force on a moving charge F = q v B sin(theta) and on a current-carrying conductor F = B I L sin(theta), including the right-hand rule, circular motion of charged particles in uniform magnetic fields, and forces between parallel conductors

Magnetic forces. Applies F = q v B and F = B I L with the right-hand rule, derives the circular motion of a charge in a uniform field, and works the standard cyclotron-radius and parallel-conductor examples QCAA uses in IA1 and EA Paper 2.

11 min read →

Apply Coulomb's law F = k q1 q2 / r^2, the electric field of a point charge E = k Q / r^2, and the uniform electric field between parallel plates E = V / d to calculate forces, fields and the motion of charged particles

Electric fields. Coulomb's law for the force between point charges, the radial field of a point charge, the uniform field between parallel plates and its relation to potential difference, and the projectile-like motion of a charged particle accelerated across a gap.

11 min read →

Apply the ideal-transformer relationships V_s / V_p = N_s / N_p and I_p / I_s = N_s / N_p, and the role of step-up and step-down transformers in minimising I^2 R losses in AC power transmission

Transformers. Derives the ideal voltage and current ratios from Faraday's law, identifies the four real-transformer loss mechanisms with their mitigations, and explains why high-voltage AC transmission minimises line losses, with the typical Australian grid step-up and step-down chain.

12 min read →