EASA Module 2 Physics flashcards

32 cards. Read the term and the definition here. The deck at the top of this page is optional.

Density formula

Density is mass per unit volume, ρ = m/V; SI unit kg/m³. Relative density compares a substance's density with water's 1000 kg/m³.

Hooke's law

For a spring or elastic material, extension is directly proportional to applied force up to the elastic limit: F = kx, where k is the spring constant in N/m.

Stress and strain

Stress is force per unit cross-sectional area (σ = F/A, N/m²); strain is fractional extension (ε = ΔL/L). Young's modulus E = σ/ε in the linear region.

Archimedes' principle

The upthrust on a body in a fluid equals the weight of fluid displaced: F = ρ_fluid × V_displaced × g. It causes floating when upthrust equals weight.

Elastic vs plastic deformation

Elastic deformation is reversible: the material returns to its original shape when the load is removed. Plastic deformation is permanent and occurs beyond the elastic limit.

Viscosity

Viscosity is a fluid's internal resistance to flow, caused by friction between layers. It decreases with temperature in liquids but increases with temperature in gases.

Equations of motion

For constant acceleration: v = u + at, s = ut + ½at², v² = u² + 2as, and s = (u+v)t/2.

Newton's second law

The resultant force on a body equals mass times acceleration: F = ma. Weight is the gravitational force W = mg, with g ≈ 9.81 m/s².

Moment of a force

Moment = force × perpendicular distance from the pivot, measured in N·m. A body is in rotational equilibrium when clockwise moments equal anticlockwise moments.

Conservation of momentum

In an isolated system with no external resultant force, total momentum (p = mv) before an interaction equals total momentum after it.

Work, energy and power

Work W = Fs cosθ; kinetic energy = ½mv²; gravitational potential energy = mgh; power = work done per second, P = W/t.

Continuity equation

For incompressible flow in a pipe, the volume flow rate is constant: A₁v₁ = A₂v₂, so a narrower section has a higher flow speed.

Bernoulli's equation

Along a streamline in steady, ideal flow: p + ½ρv² + ρgh = constant. Higher flow speed means lower static pressure.

Reynolds number

Re = ρvd/η compares inertial to viscous forces. Low Re indicates laminar flow; high Re indicates turbulent flow.

Celsius to kelvin

Absolute temperature T(K) = θ(°C) + 273.15. The kelvin scale starts at absolute zero, where particle kinetic energy is minimal.

Specific heat capacity

Heat needed to raise a mass's temperature: Q = mcΔT, where c is specific heat capacity in J/(kg·K).

Latent heat

Energy to change phase without temperature change: Q = mL, where L is specific latent heat in J/kg (fusion or vaporisation).

Ideal gas law

PV = nRT, with R = 8.314 J/(mol·K). Combined form: P₁V₁/T₁ = P₂V₂/T₂ for a fixed mass of gas.

First law of thermodynamics

ΔU = Q − W, where Q is heat added to the gas and W is work done by the gas. Internal energy changes by heat flow and work.

Heat transfer methods

Conduction transfers heat through solids by molecular collisions; convection circulates fluids by density differences; radiation transfers energy as infrared without a medium.

Wave equation

Wave speed equals frequency times wavelength: v = fλ. Period is the reciprocal of frequency, T = 1/f.

Transverse vs longitudinal

In transverse waves particles oscillate perpendicular to propagation (light, string waves); in longitudinal waves they oscillate parallel (sound).

Speed of sound in air

About 343 m/s at 20 °C, increasing roughly 0.6 m/s per °C rise; it is much faster in water (~1500 m/s) and steel.

Standing waves on a string

Fixed ends create nodes; the fundamental has wavelength 2L, giving f = v/(2L). Harmonics are integer multiples of this frequency.

Doppler effect

The observed frequency increases when source and observer approach and decreases when they recede; the shift depends on relative speed.

Sound intensity level

Intensity I = P/(4πr²) for a point source. 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 of the same size.

Refractive index

n = c/v, where c is light speed in vacuum and v in the medium. Higher n means slower light and more bending.

Snell's law

n₁ sin θ₁ = n₂ sin θ₂, relating angles of incidence and refraction measured from the normal at a boundary.

Critical angle

For light going from denser to less dense medium, sin θc = n₂/n₁. Beyond θc total internal reflection occurs.

Thin lens equation

1/f = 1/v + 1/u with sign conventions; magnification m = v/u = image height/object height. A converging lens has positive focal length.

Dispersion of light

Refractive index varies with wavelength, so white light splits in a prism; violet slows more and bends more than red.