P1.1 and P1.2 Changes in Energy Stores + Conservat
- Energy can be stored in a variety of different energy stores
- Energy is transferred by heating, by waves, by an electric current, or by a force when it moves an object
- When an object falls and gains speed, its store of GPE decreases and its kinetic energy store increases.
- When a falling object hits the ground without bouncing back, it's kinetic energy store decreases. Some or all of its energy is transferred t the surroundings - the thermal energy store of the surroundings increases, and energy is also transferred by soundwaves.
- Energy cannot be created or destroyed.
- Conservation of energy applies to all energy changes.
- A closed system is a system whch no energy transfers take place out of or into the energy stores of the system
- Energy can be transferred between energy stores within a closed system. The total energy of the system is always the same, before and after, any such transfers.
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P1.3 and P1.4 Energy and Work + GPE stores
- Work is done on an object when a force makes the object move.
- Energy Transferred = Work Done
- Work done, W (joules, J) = Force applied, F (newtons, N) x distance moved along the line of action of the force, s (metres, m)
- Work done to overcome friction is transferred as energy to the thermal energy stores of the objects that rub together and to the surroundings.
- The GPE store of an object increases when it moves up and decreases when it moves down.
- The gravitational potential energy store of an object increases when it is lifted up because work is done on it to overcome the gravitational force.
- The gravitational field strength on the moon is less than on the earth.
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P1.5 Kinetic energy + elastic energy stores
- The energy in the kinetic energy store of a moving object depends on its mass and its speed.
- The kinetic energy store of an object is Kinetic Energy = 1/2 x mass x speed^2
- Elastic Potential energy is the energy stored in an elastic object when work is done on the object.
- The elastic potential energy stored in a stretched spring is Elastic Potential energy = 1/2 x spring constant x extension^2
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