Topic 3 - Conservation of Energy

• What is the equation for gravitational potential energy? Give SI units for all quantities involved.


  Mgh

  Mass x Gravitational Field Strength x Height

  Energy (J), Mass(kg), Gravitational Field Strength (N/kg),
• What is the equation for kinetic energy? Give SI units for all quantities involved.


  ½ m v2

  ½ x Mass x (Velocity)²

  Energy (J), Mass(kg), Velocity(m/s)
• What is meant by the 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 then returns to its starting position. Ignore air resistance.


  ● Upwards: KE is converted to GPE

  ● Peak: Maximum GPE, zero KE

  ● Downwards: GPE is converted to KE
• State any changes in the total energy of a ball that is kicked, assuming that no external forces act.


  The total energy of the system remains constant due to the conservation of energy.
• Describe the energy changes that occur in a filament light-bulb

  ● Electrical energy is transferred into light and heat energy

  ● Light is a useful energy form, heat is waste energy
• Describe the energy transfers for a bungee jumper

  ● When falling, the GPE is converted to KE of jumper

  ● As the cord tightens, KE is converted and stored as Elastic Potential Energy (EPE)

  ● At lowest point, the jumper's initial GPE equals the EPE stored in the cord
• Explain why a bungee jumper slows down once the cord begins to stretch.

  ● Kinetic energy decreases since it is converted to elastic potential energy

  ● Since KE is proportional to (velocity)², as KE decreases, so does velocity.
• What is waste energy?


  The energy that is not used by the device for its desired purpose, or not converted into the desired form.
• State two equations to calculate efficiency.

  =Useful Output Energy Transfer/Total Input Energy Transfer

  =Useful Power Output/Total Power Output
• State the consequence for energy transfer of a material with a high thermal conductivity.


  The rate of energy transfer through the material is higher than for a material with a lower thermal conductivity.
• Do double-glazed windows have a higher or lower thermal conductivity than single-glazed windows?

  Lower, meaning less energy transfers through them.
• State three methods of reducing heat loss in a building.

  1. Double glazing

  2. Loft and wall insulation

  3. Thicker walls
• How can you reduce unwanted energy transfer in a mechanical system?

  Reduce friction by lubricating moving parts.
• How can the efficiency of a system be increased?

  1. Reducing waste output (by lubrication, thermal insulation etc.)

  2. Recycling waste output (eg. recycling thermal waste energy as input energy)
• What is a renewable energy resource?

  An energy source which can be replenished as it is being used up.
• Give four examples of renewable energy resources.

  1. Wind Energy

  2. Hydro-Electricity

  3. Tidal Energy

  4. Solar Energy
• Give an example of a non-renewable energy resource.

  Fossil fuels (for example coal, oil and gas).
• What are the advantages of generating power using gas rather than coal?

  ● Flexible Generation: Gas power stations have short start-up times so can be switched on/off more readily

  ● Lower emissions of carbon dioxide
• State two disadvantages of using renewable energy resources to generate power.

  ● Output often determined by external factors (like wind speed), so supply is uncertain

  ● Generating power through other means is often more efficient and economically beneficial
• Explain the environmental impacts of burning fossil fuels.

  ● Carbon Dioxide contributes to the greenhouse effect, and causes global warming

  ● Sulphur Dioxide leads to acid rain, which can damage buildings and crops
• State three advantages of fossil fuels as an energy resource.

  1. Reliable: Not dependent on external factors so can generate power anytime

  2. Can produce large amounts of energy for a given quantity

  3. Still relatively abundant, so cost-effective
• State three advantages of nuclear power.

  1. Very large amounts of energy for relatively small quantities of fuel

  2. Doesn't release greenhouse gases and so doesn't contribute to climate change

  3. Low fuel costs
• State three disadvantages of nuclear power.

  1. Produces nuclear waste which is harmful to humans & must be safely stored for centuries.

  2. Non-Renewable energy source

  3. Risk of nuclear accidents, which have fatal consequences on humans and the environment
• Give examples of social factors to consider in energy production.

  ● Visual Pollution

  ● Sound Pollution

  (both of these are disadvantages of wind farms)
• How does hydroelectric power produce energy?

  ● Rainwater collects behind a dam

  ● When this water is released, it is used

  to turn a turbine

  ● This turbine turns a generator which

  produces electricity
• What are some disadvantages of using biofuels?

  ● When plants are burned or decay they release CO2

  ● In order to grow biofuels, you need to destroy land which leads to problems because:

  ○ The land could have been natural habitats

  ○ Destroying land may involve burning plants growing on it, which would release CO2

  ● Growing biofuels reduces the land available for growing food
• What are the advantages of tidal energy sources?

  ● They do not produce greenhouse gases

  ● They are quite reliable, as tides happen twice a day

  ● They are cheap to run as tides are natural, and so are free
• What are the disadvantages of hydroelectric power?

  ● The dam may cause flooding

  ● It can cost a lot to install the required

  infrastructure
• What are some advantages of solar panels?

  ● They don't cause harm to the environment

  ● They are a renewable resource

  ● They can be used in remote areas where other types of energy are less accessible