Topic 3 - Conservation of energy Flashcards
(24 cards)
What is the equation for gravitational potential energy?
Gravitational Potential Energy (J) = Mass (kg) x Gravitational Field Strength (N/kg) x Height (m)
What is the equation for kinetic energy?
Kinetic energy (J) = 1/2 x Speed^2 ((m/s)^2)
KE = 1/2 mv^2
What is meant by conservation of energy?
- The total amount of energy in a closed system remains constant
- Energy cannot be made or destroyed but can change from one form to another
Describe the energy changes involved when a ball is thrown upwards and returns to its starting position (ignore air resistance)
- As it travels upwards, KE is converted to GPE
- At its peak, there is a maximum GPE and zero KE
- As it travels downwards, GPE is converted to KE
What changes to the total energy of a ball that is kicked if no external forces act?
The total energy of the system remains constant due to the conservation of energy
At what point does a mechanical process become wasteful
When they cause a rise in temperature so dissipating energy in heating the surroundings
Describe the energy changes that occur in a filament light-bulb
- Electrical energy is transferred into light and heat energy
- Light is useful energy form, heat is waste energy
What are ways to reduce unwanted energy transfer
- Lubrication
- Thermal insulation
How can you reduce heat loss in a builiding?
- Double glazing windows
- Loft and wall insulation
- Thicker walls
What is the equation for efficiency
Efficiency = Useful energy / Total energy
How can you increase efficiency?
- Reducing waste output (lubrication, thermal insulation etc.)
- Recycling waste output (e.g. recycling thermal waste energy as input energy)
What are main energy sources available for use on Earth?
- Fossil fuels
- Nuclear fuel
- Bio-fuel
- Wind
- Hydro-electricity
- Tides
- Sun (Solar
What are advantages of using gas to generate power instead of coal
- Flexible generation: Gas power stations have short start-up times so can be switched on/off more readily
- Lower emissions of carbon dioxide
What are disadvantages of using renewable energy resources to generate power
- Output often determined by external factors (like wind speed so supply is uncertain
- Often produce less energy per kg so less economical
What are the environmental impacts of burning fossil fuels?
- Carbon dioxide contributes to greenhouse effect and causes global warming
- Sulphur dioxide leads to acid rain which can damage buildings and crops
What are advantages of fossil fuels as an energy resource
- Reliable; not dependant on external factors
- Produce large amounts of energy per kg
- Still relatively abundant, so is cost-effective
What are advantages of nuclear power?
- Large amounts of energy per kg of fuel
- No greenhouse gases released, so doesn’t contribute to climate change
- Low fuel costs
What are disadvantages of nuclear power
- Produces nuclear waste which is harmful to humans & must be safely stored for centuries
- Risk of nuclear accidents which have fatal consequences on humans and the environment
What are social factors to consider in energy production
- Visual Pollution
- Sound Pollution
How does hydroelectric power produce energy
Rainwater collects behind a dam, when it is released, it is used to turn a turbine. This turbine turns a generator which produces electricity
What are disadvantages of using biofuels?
- When plants are burned/decay they release CO2
*In order to grow biofuels you need to destroy land which causes habitat destruction and releases CO2 when plants are cleared - Growing biofuels reduces land available for food crops
What are advantages of tidal energy sources
- No greenhouse gases
- Fairly reliable - tides occur twice a day
- Cheap to run as tides are natural hence free
What are disadvantages of hydroelectric power
- Dam may cause flooding
- Can cost a lot to install required infrastructure
What are advantages of solar panels
- Don’t harm environment
- Renewable
- Can be used in remote areas where other types of energy are less accessible
