P1 - Energy stores and systems

energy is transferred between stores
1. when energy is transferred to an object the energy is stored in one the objects energy stores
2. these energy stores are : 1. thermal energy stores 2. kinetic energy stores 3. Gravitational potential energy stores 4. elastic potential energy store 5. chemical energy stores 6. magnetic energy stores 7. electrostatic energy stores 8. nuclear energy stores.
3. energy is transferred mechanically (by a force doing work), electrically (work done by moving charges), heating or by radiation (light or sound)
when a system changes, energy is transferred
1. system = fancy word for a single object (e.g the air in a piston) or a group of objects ( e.g two colliding vehicles) that you're interested in.
2. when a system changes, energy is transferred. It can be transferred into or away from the system, between different objects in the system or between different types of energy stores
3. Closed systems are systems where neither matter nor energy can enter or leave. The net change in the total energy or a closed system is always zero.
Energy can be transferred by heating
1. take the example of boiling water in a kettle - think of the water as the system.
  1. energy is transferred to the water (from the kettle's heating element) by heating, into the water's thermal energy store (causing the temperature of the water to rise)
2. you can also think of the kettle's heating element and water together as a 2 object system.
  1. energy is transferred electrically to the thermal energy store of the kettle's heating element, which transfers energy by heating to the water's thermal energy store.
energy can be transferred by doing work
1. work done is another way of saying energy transferred - they're the same thing.
2. work can be done when current flows or by a force moving an object.
3. the initial force exerted by a person to throw a ball upwards does work. it cuases an energy transfer from the chemical energy store of the person's arm to the kinetic energy store of the ball and arm.
4. A ball dropped from height is accelerated by gravity. the gravitational force does work. it causes energy to be transferred from the ball's gravitational potential energy store to it's kinetic energy store.
5. in a collision between a car and a stationary object, the normal contact force between the car and the object does work. It causes energy to be transferred from the car's kinetic energy store to another energy store
movement means energy in an object's kinetic energy store.
1. anything that's moving has energy in its kinetic energy store. energy is transferred to this store when an object speeds up and is transferred away from this store when an object slows down
2. the energy in the kinetic energy store depends on the object's mass and speed. the greater its mass and the faster it's going, the more energy there will be in its kinetic energy store.
3. FORMULA - Ek = 1/2mv2
  1. kinetic energy (J)= 1/2 x mass(kg) x speed2 (m/s2)
raised objects store energy in the gravitational potential energy store
1. lifting an object in a gravitational field requires work. this causes a transfer of energy to the gravitational potential energy store of the raised object. the higher the object is lifted, the more energy is transferred to this store.
2. the amount of energy in the g.p.e store depends on the object's mass, its height and the strength of the gravitational field of the object is in
3. EQUATION - Ep = mgh
  1. g.p.e (J) = Mass (kg) x gravitation field strength (N/kg) x Height (m)
falling objects transfer energy
1. when something falls, energy from its gravitational potential energy store is transferred to its kinetic energy store
2. for a falling object when there's no air resistance: energy lost from the g.p.e store = energy gained in the kinetic energy store
3. in real life, air resistance acts against all falling objects - it causes energy to be transferred to other energy stores,
  1. e.g the thermal energy stores of the object and surroundings
stretching transfers energy to the elastic potential energy stores
1. stretching or squashing an object can transfer energy to its elastic potential energy store
2. as long as the limit of proportionality hasn't been exceeded energy in the elastic potential energy store of a stretched spring can be found.
3. EQUATION - Ee = 1/2ke2
  1. Elastic potential energy(J) = 1/2 x spring constant(N/m) x (extension)2 (m)2

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P1 - Energy stores and systems

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