Physics - Mechanics, Waves, Electricity and Heat
Core areas
Mechanics: kinematic equations, Newton's three laws, friction, circular motion, work–energy theorem, conservation of momentum. Gravitation and simple harmonic motion; wave motion and sound; geometric optics (mirrors, lenses, refraction); thermal physics (heat, specific heat, expansion); electricity - Ohm's law, series and parallel networks, heating effect, power; magnetism and electromagnetic induction; plus units, dimensions and measurement.
Traps
- g may be taken as 9.8 or 10 m/s²; follow the paper's instruction and stay consistent.
- Mass vs weight, distance vs displacement, speed vs velocity - scalar/vector labels are frequently swapped in the options.
- Action–reaction pairs act on different bodies, so they never cancel each other.
- Parallel resistance is always smaller than the smallest branch; series resistances simply add.
- Power has three forms - P = VI = I²R = V²/R - and the correct one depends on what is held constant.
- Sign conventions for mirrors and lenses, and real versus virtual images.
Rule of thumb
Before calculating, list the knowns with symbols and units, then choose the equation containing only those symbols plus the unknown. Dimensional analysis kills most distractors instantly: if an option's units are not those of the asked quantity, it is wrong.
Worked example: 6 Ω and 3 Ω in parallel give 1/R = 1/6 + 1/3 = 1/2, so R = 2 Ω - smaller than 3 Ω, as a parallel combination must be.