Physics

Matter exists as solid, liquid or gas. Atoms consist of protons and neutrons in a nucleus with orbiting electrons. Density ρ = mass/volume; relative density (specific gravity) compares a substance's density with water (1000 kg/m³). SI base units you must know: metre, kilogram, second, ampere, kelvin.

Force = mass × acceleration (N). A moment = force × perpendicular distance (Nm); for equilibrium the sum of forces and the sum of moments are both zero — this underpins weight-and-balance calculations. Stress = force/area (N/m² or psi), strain = extension/original length, and Young's Modulus E = stress/strain. Hooke's law applies up to the elastic limit.

Newton's three laws govern motion. Work = force × distance (joules); Power = work/time (watts); Kinetic energy = ½mv²; Potential energy = mgh. Momentum = mv and is conserved in collisions. Centripetal force F = mv²/r acts toward the centre of a turn.

Pressure = force/area. Pascal's law: pressure applied to a confined fluid acts equally in all directions — the basis of hydraulic systems and of the force multiplication in a jack. Bernoulli: in a streamline flow the total energy is constant, so where velocity increases static pressure falls. Archimedes: upthrust equals the weight of fluid displaced.

Heat transfers by conduction, convection and radiation. Specific heat capacity is the energy to raise 1 kg by 1 K. Latent heat changes state without a temperature change. Gas laws: Boyle (P ∝ 1/V at constant T), Charles (V ∝ T at constant P), and the combined law PV/T = constant. Absolute zero is 0 K = −273 °C.

Light travels in straight lines, reflects at equal angles and refracts when changing medium — the principle behind fibre optics used in aircraft data buses. Sound is a longitudinal pressure wave (~340 m/s in air at sea level). Wave speed v = f × λ. Resonance occurs when a forced vibration matches a natural frequency — a key concern in structures and engine mounts.