P1 - Energy Flashcards
What is energy?
The capacity of something to do work.
What is the law of conservation of energy?
Energy cannot be created or destroyed, only transferred into other stores.
What is dissipation?
Transfer of energy into less useful forms.
How is work done calculated?
Work done (j) = force (N) x distance (m)
How is power calculated?
Power = work done ÷ time
ALSO,
Power = (force x distance) ÷ time
What is power?
The rate at which energy is transferred / work is done.
What does work done mean?
When a force causes an object to move through a distance, work is done on the object.
What is efficiency?
The proportion of energy that is in a useful energy store after a change in a system.
How is efficiency calculated?
Useful power/energy output
——————————————
Total power/energy input
How is percentage efficiency calculated?
Useful power/energy output
—————————————— X 100
Total power/energy input
What is temperature?
A measure of the average kinetic energy of particles in a substance.
NOT the thermal energy store of the substance.
How does the mass of a substance effect the temperature change?
The greater the mass, the more energy is needed to increase the temperature.
What are all the energy stores?
- Thermal
- Kinetic
- Gravitational potential
- Elastic potential
- Chemical
- Magnetic
- Electrostatic
- Nuclear
What is the thermal energy store?
The total kinetic energy stored in all the particles of an object.
What is the kinetic energy store?
The energy an object has because it is moving.
How is kinetic energy calculated?
KE = 0.5 x m x v²
KE (j) = 0.5 x mass (kg) x speed² (m/s)
What is the gravitational potential energy store?
Energy stored in an object due to its position in a gravitational field.
How is gravitational potential energy calculated?
GPE = mgh
GPE = mass (kg) x gravitational field strength (N/kg) x height (m)
What is the gravitational field strength on earth?
9.8
What is the elastic potential energy store?
The energy an object has when it is stretched or compressed.
How is elastic potential energy calculated?
EPE = 0.5 x k x e²
EPE = 0.5 x spring constant (N/m) x extension² (m)
What is the chemical energy store?
The energy stored in fuels, food, or batteries that can be transferred by chemical reactions.
What is the magnetic energy store?
What is the electrostatic energy store?
Energy stored when repelling charges move closer together
OR when attracting charges pull further apart.
