Energy Transfers Flashcards
(30 cards)
Equation for gravitational potential energy
GPE = mass (kg) x gravitation field strength (N/kg) x height
Equation for Kinetic energy
1/2 x mass x (velocity)^2
1/2 x m x v^2
Velocity(m/s)
What is meant by conservation of energy
Total amounts of energy in a closed system that remains constant
Energy cannot be made of destroyed by can change from one form to another
Describe energy changes involved when a ball is thrown upwards and then returns to starting position
Upwards : KE is converted to GPE
Peak : Maximum GPE, zero KE
Downwards : GPE is converted to KE
State any changes in the totals energy of a ball that is kicked, assuming 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 the jumper
As the cord tightens the KE is converted and stored as elastic potential energy (EPE)
At lowest point the jumpers initial GPE equals the EPE stored in the cord
Explain why a bungee jumper slows down once the cord begins to stretch
KE 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
Energy that is not used by the device for its desired purpose, or not converted into the desired form
Two equations to calculate efficiency
Useful output energy / total input energy
Useful power output / total power output
State the consequence for energy transfers of a material with a night thermos 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 deducting heat loss in a building
- Double glazing
- Loft and wall insulation
- 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
- Reducing waste output
- Recycling waste output
What is a renewable energy resource
An energy source which can be replenished as it is being used up
Four examples of renewable energy resources
- Wind energy
- Hydro electricity
- Tidal energy
- Solar energy
Example of a non renewable energy resource
Fossil fuels
What are the advantages of generating power using gas rather than coal
Flexible generation : gas power stations have short start up times
Lower emission of carbon dioxide
Two disadvantages of using renewable energy resources to generate power
Output often determined by external factors so supply is uncertain
Renewable fuel often produce less energy per kg
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
Three advantages of fossil fuels as an energy resource
Reliable
Produce large amounts of energy per kg
Still relatively abundant so cost effective
Three advantages of nuclear power
Very large amounts of energy per kg
No greenhouse gases released
Low fuel costs
Three disadvantages of nuclear power
Produces nuclear waste
Non renewable energy source
Risk of nuclear accidents
