Physics 1

• .Energy is stored in systems

  . Energy cannot be created it can only be stored or transferred.
• The amount of energy transferred is usually called the work done
• The energy stores are: kinetic, gravitational potential, elastic potential, magnetic, nuclear, chemical, electrostatic and thermal
• Objects have more thermal energy in their thermal energy store when their temperature increases
• Objects raised against the pull of gravity have energy in their gravitational potential energy store.
• Objects with chemical bonds have energy in their chemical energy stores.
• Moving objects have energy in their kinetic energy store.
• Objects being stretched or squashed have energy in their elastic potential energy store.
• When magnetic materials attract or repel each other they have energy in their magnetic energy stores.
• When charged particles attract or repel each other they have energy in their electrostatic energy store.
• Atomic nuclei have energy in their nuclear energy store.
• Energy can be transferred in different directions.
• Energy can be transferred in or out of a system, between different objects in a system and between different energy stores
• kinetic energy = 0.5 x mass x speed squared
• Elastic potential energy= 1/2 x spring constant x extension squared
• Gravitational potential energy= mass x gravitational field strength x height
• Some systems need more energy than others to warm up
• Systems warm up when energy is transferred to their thermal energy store and systems cool down when this energy is transferred out the store.
• Specific heat capacity is the amount of energy needed to raise the temperature of 1kg of a substance by 1 degree
• Change in thermal energy = mass x specific heat capacity x change in temperature
• Power is the rate of energy transfer, measured in watts.
• Power is measured in watts(W)
• Power = energy transferred / time taken to transfer energy (Watts) or power=work done/time taken to do work (Joules)
• Dissipated means when energy transferred to less useful energy stores, it is “wasted”
• A closed system is where energy cannot enter or leave the system
• In a closed system energy can be transferred usefully, stored or dissipated
• The total amount of energy in a closed system always remains the same.
• Lubrication helps to prevent energy being wasted.
• Lubrication usually involves spreading an oily substance over the parts of a mechanical system.
• Lubrication reduces friction between objects when they move ~> more energy is transferred to kinetic energy store than thermal energy store.
• Thermal energy can be transferred by conduction ~> in conduction vibrating particles transfer energy to neighbouring particles
• Conduction allows energy to be spread across the entire body of a material.
• Thermal conductivity is a measure of how quickly a material can transfer energy by conduction.
• Thermal insulation helps to prevent energy being wasted By conduction
• Efficiency = useful output energy/total input energy
• A renewable resource is one that is replenished as it is used , meaning it can never run out.
• A non renewable resource is one that cannot be replenished as it is used, meaning it will eventually run out
• Fossil fuels are reliable because they can generate lots of energy and can be burned at any time
• Tidal energy is reliable as the tide goes in and out everyday
• Solar and wind arent reliable as rely on the weather