EASA Module 2 Physics cheat sheet

Density is mass per unit volume: ρ = m/V, in kg/m³. Relative density = density of substance ÷ density of water (1000 kg/m³).

Pressure is force per unit area: p = F/A, in pascals (1 Pa = 1 N/m²). In a static fluid, pressure increases with depth: p = ρgh.

Hooke's law: extension is proportional to load up to the elastic limit, F = kx, where k is the spring constant in N/m.

Stress σ = F/A (N/m²) and strain ε = ΔL/L (dimensionless); Young's modulus E = σ/ε applies in the linear elastic region.

Elastic deformation is reversible; plastic deformation is permanent. Beyond the elastic limit Hooke's law no longer applies and the material may fracture.

Solids have fixed shape and volume, liquids fixed volume only, gases neither; particle spacing, ordering and kinetic energy explain these properties.

Archimedes' principle: upthrust on a submerged or floating body equals the weight of fluid displaced, F = ρ_fluid × V_displaced × g.

Viscosity is a fluid's internal resistance to flow. It decreases with rising temperature in liquids and increases with rising temperature in gases.

Equilibrium requires zero resultant force and zero resultant moment. For moments about any point: sum of clockwise moments = sum of anticlockwise moments.

Moment of a force = force × perpendicular distance from the pivot (N·m). A couple produces moment F × d, where d is the separation of the forces.

Constant-acceleration kinematics: v = u + at; s = ut + ½at²; v² = u² + 2as; s = (u + v)t/2.

Newton's second law: resultant force F = ma. Weight is W = mg, using g ≈ 9.81 m/s² near the Earth's surface.

Momentum p = mv; impulse Ft = Δp. Total momentum is conserved in an isolated system with no external resultant force.

Work W = Fs cosθ; kinetic energy = ½mv²; gravitational potential energy = mgh; power P = W/t = Fv.

Continuity for incompressible flow: A₁v₁ = A₂v₂, so flow speed rises where the pipe cross-section narrows.

Bernoulli's equation for steady ideal flow along a streamline: p + ½ρv² + ρgh = constant; higher speed corresponds to lower static pressure.

Reynolds number Re = ρvd/η indicates flow regime: low Re gives laminar flow, high Re gives turbulent flow.

Absolute temperature: T(K) = θ(°C) + 273.15. Absolute zero (0 K) is the lowest attainable temperature.

Sensible heat: Q = mcΔT, where c is specific heat capacity in J/(kg·K).

Latent heat: Q = mL for a phase change at constant temperature, where L is specific latent heat of fusion or vaporisation in J/kg.

Thermal expansion: ΔL = LαΔT for length; ΔV = VγΔT for volume, with γ ≈ 3α for isotropic solids.

Ideal gas law: PV = nRT with R = 8.314 J/(mol·K); for fixed mass, P₁V₁/T₁ = P₂V₂/T₂.

First law of thermodynamics: ΔU = Q − W, where Q is heat supplied to the system and W is work done by the system.

Conduction transfers heat through solids by molecular collisions; convection circulates fluids via density differences; radiation transfers energy as infrared and needs no medium.

Heat engine efficiency η = useful work output ÷ heat input; the Carnot limit is η ≤ 1 − T_cold/T_hot with temperatures in kelvin.

Wave equation: v = fλ. Period and frequency are reciprocals: T = 1/f.

Transverse waves oscillate perpendicular to propagation (light, waves on a string); longitudinal waves oscillate parallel to propagation (sound).

Speed of sound in air is about 343 m/s at 20 °C and rises with temperature; it is roughly 1500 m/s in water and about 5000 m/s in steel.

Frequency determines pitch, amplitude determines loudness, and harmonic content determines timbre of a sound.

Reflection, refraction, diffraction and interference apply to waves; noticeable diffraction occurs when the gap size is comparable to the wavelength.

Standing waves on a string fixed at both ends: nodes at the ends, fundamental wavelength 2L, fundamental frequency f = v/(2L).

Doppler effect: observed frequency is higher when source and observer approach, lower when they recede.

Sound intensity from a point source: I = P/(4πr²). Intensity level in decibels: dB = 10 log₁₀(I/I₀), with I₀ = 1×10⁻¹² W/m².

Law of reflection: angle of incidence equals angle of reflection, both measured from the normal; a plane mirror forms a virtual, laterally inverted image.

Refractive index n = c/v, where c = 3.00×10⁸ m/s is the speed of light in vacuum and v is the speed in the medium.

Snell's law: n₁ sin θ₁ = n₂ sin θ₂, with angles measured from the normal at the boundary.

Critical angle for a denser-to-less-dense boundary: sin θ_c = n₂/n₁; total internal reflection occurs when the incidence angle exceeds θ_c.

Thin lens equation: 1/f = 1/v + 1/u with a consistent sign convention; magnification m = v/u = image height ÷ object height.

A converging lens has positive focal length and forms a real image when the object lies beyond the focal point; a diverging lens has negative focal length.

Dispersion occurs because refractive index varies with wavelength; in a prism violet light bends more than red light.

Electromagnetic spectrum order of increasing frequency: radio, microwave, infrared, visible, ultraviolet, X-ray, gamma ray. Optical fibres guide light by total internal reflection, with cladding of lower refractive index.