Topic 3 Conservation of Energy

• Change in gravitational potential energy(J) = mass(kg) x gravitational field strength(N/kg) x height(m)
• Kinetic energy(J) = 1/2 * Mass (kg) * Velocity^2 (m/s^2)
• Conservation of Energy: Energy cannot be created or destroyed it can only be transferred from one store to another
• Energy stored in food, fuel and batteries is chemical energy
• energy stored in moving objects is kinetic energy
• energy stored in hot objects is thermal energy
• energy stored in stretched or squashed or twisted materials is elastic potential energy/strain energy
• objects in high positions is gravitational potential energy
• Energy stored inside atoms is atomic or nuclear energy
• If an object is projected into the air, as it rises higher kinetic energy will be changed into gravitational potential energy
• A moving object will start off with kinetic energy. Once it hits an obstacle, the kinetic energy may be transferred to the surroundings as thermal energy and sound waves. Some of the kinetic energy of the moving object can even be transferred to the obstacle, causing it to move.
• When an object is accelerated by a force, there is a transfer of energy. Firstly, energy is required to accelerate the object; this could be chemical, thermal or electrical (the situation will determine the specific type of energy). This energy will then be converted into kinetic energy (used to accelerate the object).
• To slow down the vehicle, the kinetic energy of the movement will be transferred into another store of energy. This energy could be sound waves and thermal energy.
• When we are heating up water in an electric kettle, we are transferring electrical energy into thermal energy, which is used to heat up the water.
• Where there are energy transfers in a closed system there is no net change to the total energy in that system
• Open systems are able to exchange energy and matter with their surroundings.
• A Closed energy system is unable to exchange energy and matter with their surroundings.
• Mechanical processes become wasteful when they cause a rise in temperature so dissipating energy in heating the surroundings
• In all system changes energy is dissipated so that it is stored in less useful ways. An example would be a lightbulb (thermal energy)
• when two moving parts touch friction causes them to heat up. This thermal energy is wasted so this can be reduced using lubrication
• Insulation slows down the rate at which energy is transferred out of a house by heating
• The rate of energy transfer is reduced by increasing thickness and decreasing thermal conductivity. This means that it takes longer for the building to cool
• efficiency = useful energy/total energy supplied
• efficiency can be increased by reducing wasted energy transfers so more of the input energy is usefully transferred
• the main energy sources available for use on earth are fossil fuels, nuclear fuel, bio-fuel, wind, hydroelectricity, the tides and the sun
• Releasing energy from some stores causes pollution and harmful waste products. Burning fossil fuels releases carbon dioxide, adding to the greenhouse effect, and sulfur dioxide which causes acid rain.
• A renewable energy resource is one that is being (or can be) replenished as fast (or faster) than it is used.
• Fossil fuels are non renewable, have high power output and release CO2
• Nuclear fuels are non renewable, have very high power output and release radioactive waste
• Bio-fuels are renewable, have medium power output and have low impact
• wind energy is renewable, has very low power output and take large amount of space up
• hydroelectricity is renewable, has medium power output and local habitats are affected by the dams built
• Geothermal energy is renewable has medium power output and has a very low impact on the earth
• tides are renewable, have potentially very high power output but is hard to harness and tidal barrages can block sewage
• the sun's energy is renewable, have potentially very high power output and has a very little impact
• water waves energy is renewable, have low power output and has a very little impact
• Demand for energy varies with the time of year and the time of day. During early evenings a lot of energy is needed for heating, lighting and cooking but overnight there is very little needed while people sleep.