PHYSICS PAPER 1

• energy is never created or destroyed only transferred
• energy stores: thermal (heat)
• energy stores: kinetic (moving)
• energy stores: gravitational potential (height)
• energy stores: elastic potential (strech)
• energy stores: chemical (body)
• energy stores: magnetic (attraction)
• energy stores: electrostatic (electrons)
• energy stores: nuclear (boom)
• Mechanical work done: force needed to move an object
• Electrical work done: energy required to overcome the resistance of the wires in the circuit
• kinetic energy: 1/2 mv^2
• kinetic energy : energy possessed due to motion
• kinetic energy: depends on speed and mass ( faster objects have more kinetic energy) (heavier objects have more kinetic energy)
• Gravity: force of attraction between two objects
• GPE: Mass x gravitational field strength x height
• gravitational field ( influence of gravity around an object)
• if an object interacts with a gravitational field it experiences a force creating a force of attraction (weight)
• Weight = Mass x Gravitational field strength
• conservation of energy : energy cant be created of destroyed but can be transferred, stored or dissipated
• open system —> energy and matter can freely move in the environment vs environment (outside the system)
• closed system energy and matter cant enter or leave the system
• heat is transferred by conduction (solids), convection (fluids: liquids and gases) or radiation ( empty space )
• Conduction: vibrating particles transfer energy to neighboring particles
• thermal conductivity : metals have a high thermal conductivity as plastics and fluids have a low thermal conductivity
• thermal conductivity: how well objects can transfer thermal energy through conduction
• convection: particles move away from warmer region to cooler region making them more spread out making them less dense and more spread out
• convection current: in oceans and buildings (radiators)
• to reduce convection stop the free flow of fluids
• radiation: infra-red waves
• hotter the object more radiation it emits
• House is sealed so air cant leave —> which loses heat through convection
• reduce heat loss by conduction: thick walls, materials will low thermal conductivity, cavity walls, air gap ( air is a poor conductor) filled with insulating foam
• windows—> glazing single or (double) have different layers of glass with a small air gap reducing conduction
• reduce friction in houses too: reduces the efficiency of energy transfer
• power: rate of energy transferred p= e/t
• power: rate of work done p= wd/t
• efficiency: the ratio of useful energy output to the total energy input, expressed as a percentage
• efficiency= useful energy (or power) output / total energy (or power) input
• no object is 100% efficient energy is usually transferred as thermal energy