AQA Physics P1 - Energy

Energy can be stored in different ways and is transferred by heating, waves, an electric current, or when a force moves an object. Here are some examples:

• Chemical energy stores include fuels, foods, or the chemicals found in batteries. The energy is transferred during chemical reactions.
• Kinetic energy stores describe the energy an object has becuase it is moving.
• Gravitational potential energy stores are used to describe the energy stored in an object because of its position, such as an object above the ground.
• Elastic potential energy stores describe the energy stored in a springy object when you stretch or squash it.
• Thermal energy stores desrcibe the energy a substance has because of its temperature.

Energy can be transferred from one store to another. For example, a torch's battery pushes a current thorugh the bulb. This makes the torch bulb emit light, as well as emit heat. Another classic one is an electric kettle. When an electric kettle is used to boil water, the current in the kettle's heating element transfers energy to the thermal energy store of the water and the kettle. Another common transfer which is seen often is when an object is thrown into the air. The object slows down as it goes up and here is when energy is transferred from the objects kinetic energy store to its gravitational potential energy store.

work done, W = force applied, F x distance, s (metres,m)

weight = mass x gravitational field strength

gravitational potential energy = mass x gravitational field strength x height

power = work done/energy transferred divided time

efficiency = useful power output x total power output

energy transferred = power x time

kinetic energy = 0.5 x mass x (speed) squared 

efficiency = useful output energy transfer divided useful input energy transfer

elastic potential energy = 0.5 x spring constant x extension squared