IGCSE›Edexcel IGCSE Physics›Mind mapsDensity & PressureEdexcel IGCSE Physics: Mind mapStudy pack PDFAlso for this subtopic:Revision notesFlashcardsSubtopic testCover factsDensityMass per unit volume of a substanceρ=mV\rho = \frac{m}{V}ρ=VmUnit is kg/m³High density = lots of mass in small volumeMeasuring densityMass from a balanceLiquid volume from a measuring cylinderIrregular solid volume by displacementThen apply ρ=m/V\rho = m/Vρ=m/VPressureForce per unit areap=FAp = \frac{F}{A}p=AFUnit is the pascal (Pa)Smaller area → larger pressureSharp blades cut easily; snowshoes stop sinkingDensityand pressureρ\rhoρPakg/m³Fluid pressureActs equally in all directions at a pointCaused by random collisions of moleculesIncreases with depth: more weight abovep=hρgp = h\rho gp=hρgWorked examplePressure at 5 m depth in waterp=5×1000×10p = 5 \times 1000 \times 10p=5×1000×10Answer: 50 000 PaExam tipsConvert cm³ to m³ (divide by 1 000 000)Convert g to kg (divide by 1000)hρgh\rho ghρg is the liquid's contribution onlyAdd atmospheric pressure for total at depth