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Formula for gravitational potential energy
Gravitational potential energy=mass x gravitational field strength x change in height
Formula for kinetic energy
Kinetic energy=1/2 x mass x speed²
What is the conservation of energy?
Energy cannot be created or destroyed, only transferred from one store to another. In a closed system, the total amount of energy remains constant
Describe the energy changes in an object thrown upwards (ignoring air resistance)
As the object goes upwards, KE is converted to GPE. At the maximum height of the throw, the object has maximum GPE and no KE (as it is not moving). When it is going downward, GPE is converted to KE again - KE is at a maximum and GPE is at a minimum when the object is just about to hit the floor.
Describe the energy changes in an object projected up a slope
KE is transferred to GPE
Describe the energy changes when a moving object hits an obstacle
KE is transferred into sound and transferred into the object being hit, which may cause it to move
Describe the energy changes in a vehicle slowing down
KE is transferred to heat/thermal energy through friction in the brakes
Describe the energy changes when water boils in a kettle
Electrical energy transfers to thermal energy, and some sound energy
When do mechanical processes become wasteful?
When they cause a rise in temperature, so energy dissipates by heating the surroundings
How does lubrication reduce unwanted energy loss?
Less heat (caused by friction) is lost to the surroundings as there is less friction, so the temperature of the process remains low - little energy is lost as heat
How does thermal insulation reduce unwanted energy transfer?
Less heat is lost to the surroundings as it is trapped in insulation
How does the thickness and thermal conductivity of the walls of a building affect its rate of cooling?
Thicker walls mean greater thermal insulation so less heat is lost (the rate of cooling decreases). Air cavities cause heat loss by convection - insulation in these cavities fill these gaps and prevent air flow, also decreasing the rate of cooling.
How can efficiency be increased?
Reducing waste output (by lubrication or thermal insulation), and recycling waste output (absorbing energy dissipated to the surroundings and then used as input heat energy)
Renewable energy sources
Wind, hydro-electricity, tidal, solar, biofuel
Non-renewable energy sources
Fossil fuels (coal, oil, gas), nuclear energy
Advantages of using natural gas to create energy
It has short start-up times so can easily be switched on or off, and there are lower carbon emissions
Disadvantages of using renewable energy sources
There is often an uncertain supply, often less efficient and less economical
Environmental impacts of burning fossil fuels
Carbon dioxide (a by-product of combustion) contributes to global warming and sulphur dioxide leads to acid rain
Advantages of fossil fuels
They are a reliable source of energy, they produce large amounts of energy, they are still relatively abundant (so are cost-effective)
Advantages of nuclear power
Large amounts of energy are produced, no greenhouse gases are emitted, fuel cost is low
Disadvantages of nuclear power
Produces toxins nuclear waste, is a non-renewable source of energy, risk of nuclear accidents or fallout
Patterns and trends in the use of energy resources
Fossil fuels used to be the main source of energy during the Industrial Revolution because they provided lots of energy and were easy to mine. Renewable energy has become more popular in recent decades due to environmental concerns and technological advancements
