energy Flashcards
What is a system?
An object or group of objects.
When a ball hits a wall some kinetic energy is…
Transferred as sound.
What is energy measured in?
Joules.
What is the equation for kinetic energy?
1/2 x mass x speed squared.
What is elastic potential?
Energy stored in a spring when it is stretched.
What is the equation for elastic potential energy?
1/2 x spring constant x extension squared.
What is spring constant measured in?
Newtons per metre.
How do you calculate gravitational potential energy?
mass x gravitational field strength x height.
What is gravitational field strength measured in?
Newtons per kilogram.
What is power measured in?
Watts.
What 2 things is power the rate of?
Energy transferred and work done.
What are the 2 equations for power?
Energy transferred. Work done.
————————— or ——————-
Time. Time
Energy transfers cannot be…
Created or destroyed.
What 3 things can happen to energy transfers?
~They can be transferred usefully
~They can be stored
~They can be dissipated
What does lubrication do?
Reduces friction so less heat energy is lost.
What are 2 ways of reducing energy waste?
Lubrication and thermal insulation.
If thermal conductivity is higher…
~Heat is allowed to travel through the material more easily
~So the rate of energy transfer by conduction across the material is higher
What is efficiency the ratio of?
Useful work done by a machine to the energy supplied to it.
What are the 2 equations for efficiency?
Useful energy output. Useful power output
—————————— or ———————————
Total energy input. Total power input
Efficiency of a system can be increased by…
~Reducing waste output
~Recycling waste output
What are the 6 renewable energy sources?
~Biofuel
~Wind
~Hydro-electricity
~Geothermal
~Tidal
~Solar
Why are some energies renewable?
As they can be replenished as they are used.
Why isn’t solar energy very reliable?
As it doesn’t work at night or in bad weather.
What are 2 examples of non-renewable energies?
Fossil fuels and nuclear fuel.
Why are non-renewable energy sources used for large scale energy supplies?
As they have a large output per kilogram.
What are the 3 main energy uses?
Transport, electricity generation and heating.
How does the extraction of energy have an impact on the environment?
~Fossil fuels involve destroying landscapes
~Wind turbines are seen as eye pollution
What do fossil fuels release?
Harmful emissions.
