PHYSICS-FORMULA-SHEET.pdf, Study notes of Physics

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Page 1 Important Equations in Physics for IGCSE course General Physics: 1 For constant motion: 푣 = 푠 푡 ‘v’ is the velocity in m/s, ‘s’ is the distance or displacement in meters and ‘t’ is the time in sec 2 For acceleration ‘a’ 푎 = 푣 − 푢 푡 u is the initial velocity, v is the final velocity and t is the time 3 Graph: in velocity-time graph the area under the graph is the total distance covered Area of a rectangular shaped graph = base × height Area of triangular shaped graph = ½ × base × height 4 Weight is the force of gravity and mass is the amount of matter 푤 = 푚 × 푔 w is the weight in newton (N), m is the mass in kg and g is acceleration due to gravity = 10 m/s2 5 Density ‘ρ’ in kg/m3 (ρ is the rhoo) 휌 = 푚 푉 m is the mass and V is the volume 6 Force F in newtons (N) 퐹 = 푚 × 푎 m is the mass and a is acceleration 7 Terminal Velocity: falling with air resistance 푊푒푖푔ℎ푡 표푓 푎푛 표푏푗푒푐푡(푑표푤푛푤푎푟푑) = 푎푖푟 푟푒푠푖푠푡푎푛푐푒 (푢푝푤푎푟푑푠) implies no net force, therefore no acceleration, constant velocity 8 Hooke’s Law 퐹 = 푘 × 푥 F is the force, x is the extension in meters and k is the spring constant 9 Moment of a force in N.m (also turning effect) 푚표푚푒푛푡 표푓 푓표푟푐푒 = 퐹 × 푑 d is the perpendicular distance from the pivot and F is the force 10 Law of moment or equilibrium 푇표푡푎푙 푐푙표푐푘푤푖푠푒 푚표푚푒푛푡 = 푡표푡푎푙 푎푛푡푖푐푙표푐푘푤푖푠푒 푚표푚푒푛푡 => 퐹 × 푑 = 퐹 × 푑 11 Conditions of Equilibrium Net force on x-axis=zero, net force on y-axis= zero, net moment=zero 11 Work done W joules (J) 푊 = 퐹 × 푑 F is the force and d is the distance covered by an object same direction 12 Kinetic Energy Ek in joules (J) 퐸 = 1 2 × 푚 × 푣 m is the mass(kg) and v is the velocity (m/s) 13 Potential Energy ∆Ep in joules (J) Δ퐸 = 푚 × 푔 × Δℎ m is mass (kg) and g is gravity and ∆h is the height from the ground 14 Law of conservation of energy: 퐿표푠푠 표푓 퐸 = 푔푎푖푛 표푓 퐸 푚 × 푔 × ℎ = 1 2 × 푚 × 푣 15 Power in watts (W) 푃 = 푤표푟푘 푑표푛푒 푡푖푚푒 푡푎푘푒푛 푃 = 퐸푛푒푟푔푦 푡푟푎푛푠푓푒푟 푡푖푚푒 푡푎푘푒푛 Power is the rate of doing work or rate of transferring the energy from one form to another 16 Efficiency: 퐸푓푓푖푐푖푒푛푐푦 = 푢푠푒푓푢푙 푒푛푒푟푔푦 표푢푡푝푢푡 푡표푡푎푙 푒푛푒푟푔푦 푖푛푝푢푡 × 100 17 Pressure p in pascal (Pa) 푝 = 퐹 퐴 F is the force in newton (N) and A is the area in m2 18 Pressure p due to liquid 푝 = 휌 × 푔 × ℎ ρ is the density in kg/m3, h is the height or depth of liquid in meters and g is the gravity 19 Atmospheric pressure P=760mmHg = 76cm Hg =1.01x105Pa 20 Energy source renewable can be reused non-renewable cannot be reused Hydroelectric eg dam, waterfall Chemical energy eg petrol, gas Geothermal eg from earth’s rock Nuclear fission eg from uranium Solar eg with solar cell Wind energy eg wind power station Tidal/wave energy eg tide in ocean Page 2 Thermal Physics: 1 Boyle’s law: Pressure and volume are inversely proportional 푝 ∝ 푉 pV=constant 푝 × 푉 = 푝 × 푉 p1 and p2 are the two pressures in Pa and V1 and V2 are the two volumes in m3 2 Thermal Expansion (Linear) L =  ×Lo × Lo is the original length in meters,  is the change in temperature in oC, L is the change in length in meters (L1- Lo) and  is the linear expansivity of the material 3 Thermal Expansion (Cubical) V =  Vo   = 3 Vo is the original volume in m3,  is the change in temperature in oC,V is the change in volume in m3 (V1- Vo) and  is the cubical expansivity of the material. 4 Charle’s Law: Volume is directly proportional to absolute temperature 푉 ∝ 푇 푉 푇 = 푐표푛푠푡푎푛푡 푉 푇 = 푉 푇 V is the volume in m3 and T is the temperature in kelvin (K). 5 Pressure Law: Pressure of gas is directly proportional to the absolute temperature 푝 ∝ 푇 푝 푇 = 푐표푛푠푡푎푛푡 푝 푇 = 푝 푇 p is the pressure in Pa and T is the temperature in Kelvin (K). 6 Gas Law (combining above laws) 푝푉 푇 = 푐표푛푠푡푎푛푡 푝 푉 푇 = 푝 푉 푇 In thermal physics the symbol θ is used for celsius scale and T is used for kelvin scale. 7 Specific Heat Capacity: Amount of heat energy required to raise the temperature of 1 kg mass by 1oC. 푐 = 푄 푚 × ∆휃 c is the specific heat capacity in J/(kg oC), Q is the heat energy supplied in joules (J), m is the mass in kg and Δθ is the change in temperature 8 Thermal Capacity: amount of heat require to raise the temperature of a substance of any mass by 1oC Thermal capacity=m×c 푇ℎ푒푟푚푎푙 푐푎푝푎푐푖푡푦 = 푄 ∆휃 The unit of thermal capacity is J/oC. 9 Specific latent heat of fusion (from solid to liquid) 퐿 = 푄 푚 Lf is the specific latent heat of fusion in J/kg or J/g, Q is the total heat in joules (J), m is the mass of liquid change from solid in kg or g. 10 Specific latent heat of vaporization (from liquid to vapour) 퐿 = 푄 푚 Lv is the specific latent heat of vaporization in J/kg or J/g, Q is the total heat in joules (J), m is the mass of vapour change from liquid in kg or g. 11 Thermal or heat transfer In solid = conduction In liquid and gas = convection and also convection current (hot matter goes up and cold matter comes down) In vacuum = radiation 12 Emitters and Radiators Dull black surface = good emitter, good radiator, bad reflector Bright shiny surface = poor emitter, poor radiator, good reflector 13 Another name for heat radiation Infrared radiation or radiant heat 14 Melting point Change solid into liquid, energy weaken the molecular bond, no change in temperature, molecules move around each other 15 Boiling point Change liquid into gas, energy break molecular bond and molecules escape the liquid, average kinetic energy increase, no change in temperature, molecule are free to move 16 Condensation Change gas to liquid, energy release, bonds become stronger 17 Solidification Change liquid to solid, energy release bonds become very strong 18 Evaporation Change liquid to gas at any temperature, temperature of liquid decreases, happens only at the surface