Topic 3 - Conservation of energy Flashcards
What is the equation for gravitational potential energy?
Mass x gravitational field strength x height
What is the equation for kinetic energy?
1/2 x mass x velocity^2
What is meant by the conservation of energy?
The total amount of energy in a closed system remains constant
Energy cannot be created or destroyed but can change from one form to another
Describe how the the energy changes involved when a ball is thrown upwards and then Returns to its starting position
Upwards : KE is converted to GPE
Peak: maximum GPE, zero KE
Downwards: GPE is converted to KE
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, GPE is converted to KE of jumper
As cord tightens, KE is converted and stored as EPE
At lowest point, the 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 into 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 energy output/total input energy
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
Double glazing
Thicker walls
Loft and wall insulation
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?
Reducing or recycling waste output
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
Wind energy
Hydro-electricity
Tidal energy
Solar energy
Give an example of a non-renewable energy source
Fossil fuels
What are the advantages of generating power using gas rather than coal?
Lower emissions of carbon dioxide
Flexible generation: gas power stations have short start-up times so can be switched on/off more readily
State two disadvantages of using renewable energy resources to generate power
Renewable fuels often produce less energy per kg (so are less economical)
Output is often determined by external factors, so supply is uncertain
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
Produce large amounts of energy for Kg
Still relatively abundant, so cost effective
Reliable: not dependent of external factors so can generate power anytime
State three advantages of nuclear power
Very large amounts of energy per Kg of fuel
No green house gases released, so doesn’t contribute to climate change
Low fuel costs
State three disadvantages of nuclear power
Produced harmful nuclear waste
Non-renewable energy source
Risk of nuclear accidents, which have fatal consequences for humans and the environment
Give examples of social factors to consider in energy production
Visual pollution
Sound pollution
How does hydroelectric power produce energy?
Rainwater collects behind a dam
When this water is released, it it used to turn a turbine
This turbine thorns a generator which produces electricity
What are some disadvantages of using biofuels?
When plants are burned/decay they release CO2
In order to grow biofuels, you need to destroy land:
Habitat destruction
CO2 release
Growing biofuels reduces the land available for food crops
What are the advantages of tidal energy sources?
No greenhouse gases
Fairly reliable
Cheap to run as tides are natural, so 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
Are a renewable resource
Can be used in remote areas where other types of energy are less accessible
