P1 Energy Flashcards
Energy
- The ability to do work
- Symbol E and measured in joules (J)
- Not something we can touch, but amount in a system can be calculated
System
- Group of interacting objects
- It’s a closed system if no energy is transferred in or out of the system
What are the 8 energy stores?
- Kinetic energy
- Elastic potential energy
- Gravitational potential energy
- Thermal energy
- Nuclear energy
- Electrostatic energy
- Magnetic energy
- Chemical energy
Law of conservation of energy
Energy is conserved -> never created or destroyed
Energy can be transferred from store to store -> some energy is wasted
What is work done?
- The energy transferred -> work done (W) = energy transferred (E)
- It’s measured in joules (J)
What are the 4 energy transfers?
- Mechanical work - Forces and waves e.g. sound
- Electrical work - electric currents
- Heating e.g. conduction and convection
- Electromagnetic radiation e.g. Light
Useful energy
The energy transferred to where it is wanted in the way it is wanted
Wasted energy
The energy that is not usefully transferred
Law of conservation of energy
Energy cannot be created or destroyed, only transferred between stores
Why does a bouncy ball not return to its starting height?
Because it is not a closed system. Energy is lost to:
- Air -> air resistance
- Floor -> heating
- The ball’s thermal energy store
What happens to wasted energy?
Dissipated to the surroundings
How to calculate work done
Work done = force (N) x distance (m)
Friction
A force that always opposes motion
Systematic error
Newton meter not set to zero at the start
Random error
Repeated measurements of the quantity give different results under the same conditions
