Application Note — Real-World Applications of Properties of Solids & Liquids — Notes

Concept	Real-World Application	Physics Principle Used
Young's modulus	Steel cables in bridges and buildings	High Y for steel (~ $2 \times 10^{11}$ Pa) prevents dangerous elongation under load
Bulk modulus	Hydraulic braking systems	Incompressibility of brake fluid (high B) ensures instant pressure transmission
Pascal's law	Hydraulic press, car lifts, dentist's chair	$F_{1}$ / $A_{1}$ = $F_{2}$ / $A_{2}$ allows large force from small input
Bernoulli's equation	Aeroplane lift, carburettor, spray gun, atomiser	High velocity air over wing → low pressure → lift force
Stokes' law / terminal velocity	Sediment settling in rivers, blood cells in plasma	v_t ∝ $r^{2}$ determines settling rate of particles
Surface tension	Water strider walking on water, detergent action	Surface tension supports weight; detergent reduces S
Capillary action	Water transport in plants (xylem), blotting paper	h = 2S cosθ / (ρgr) drives water up narrow tubes
Viscosity	Engine oil, blood viscosity in vessels	High η resists flow; Poiseuille's law governs pipe flow
Thermal conduction	Insulation in buildings, cooking vessels	K high (copper) → good conductor; K low (wood) → insulator
Stefan-Boltzmann law	Stellar temperature estimation, thermal cameras	Power ∝ $T^{4}$ allows temperature measurement from radiation