SACE Physics: motion and relativity, electricity and magnetism, light and atoms

The three Stage 2 Physics topics

The outline describes projectile motion first, so many schools begin with Topic 1. The Standard Model, which finishes Topic 3, links directly to our Particles course, and the Laws of Motion course covers the groundwork for Topic 1.

How the subject is assessed

School assessment is 70%: an Investigations Folio worth 30% (one or two practical investigations plus a science as a human endeavour investigation) and Skills and Applications Tasks worth 40% (three or four tasks, at least two supervised by the teacher). The external examination is 30%. The Board describes five levels of achievement, A to E, and the final subject result is reported from A+ to E−.

The exam is 130 minutes and can assess Stage 2 skills and understanding from all topics. Questions may require science as a human endeavour or ideas from more than one topic. The sheet supplied contains symbols of common quantities, the magnitudes of physical constants, some formulae and standard SI prefixes, so you do not have to memorise constants, but you do have to decide which formula applies.

Worked examples

Projectile range

A ball is kicked at 25 m s⁻¹ at 40° above the horizontal from level ground. Taking g = 9.8 m s⁻², the range is:

The horizontal speed is 25 cos 40° = 19.2 m s⁻¹ and the flight time is 2 × 25 sin 40° ÷ 9.8 = 3.28 s, which gives the same 63 m. Use the Projectile Motion calculator to explore how the angle changes the range.

Force on a wire in a magnetic field

A 0.15 m wire carrying 3.0 A sits at right angles to a 0.20 T field, so the force is F = BIL = 0.20 × 3.0 × 0.15 = 0.090 N. Use the right-hand rule to say which way it acts, since the direction usually earns its own mark.

Photon energy

A red photon of wavelength 620 nm carries 3.21 × 10⁻¹⁹ J, which is 2.01 eV, when you substitute the Planck constant and the speed of light from the sheet into hc over wavelength. Quote the constants from the sheet you are given, not from memory.

Practise the photon energy equation in the Light and Energy course, then press Mark:

Grades, SATAC and your ATAR

Physics is a 20-credit subject, so it can count as one of the three core subjects. A letter grade does not convert directly to a scaled score, which is why two students on the same grade can end up with slightly different ATARs.

Dates

Use the daily paper as a trial

The SACE Board posts past exams, but your school sets any trial. The free daily paper on the Year 12 Physics track is a short timed trial: 8 questions worth 25 to 35 marks, marked as you go. It is not a 130-minute SACE exam.

• It fits: circular motion, gravitational fields, electric fields, electromagnetic induction and radioactivity or atomic physics appear in the rotation.
• It does not fit: thermal physics and simple harmonic motion are not SACE Stage 2 subtopics, capacitors appear only as one example application of electric fields, and no daily paper gives you the SACE data sheet. Relativity days are rarer.
• The Year 11 Physics paper is a fast way to keep projectile and forces questions fresh.

Exam answers

Answers and a worked mark scheme arrive with each daily paper once it is marked. They are Uni-Sine's own, not official SACE Board answers or past paper solutions.

Mistakes in SACE Physics

• Using 40° where the formula needs 2θ = 80°.
• Giving a force in newtons with no direction for a magnetic force question.
• Mixing electronvolts and joules in the same line.
• Not stating the frame of reference in a relativity answer.

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