4.1 Energy

• kinectic energy = 1/2 x mass x speed ^2
• Work done = force x distance moved by object
• Energy is the ability to do work
• Power is the rate at which work is done or energy transferred.
• Efficiency is how much useful output is produced compared to input.
• Potential energy is stored energy due to an objects position or shape
• The law of conservation of energy states that energy cannot be created or destroyed, only transferred from one form to another.
• speed = (square root of) 2 x kinetic energy / mass

  • in relation to kinetic energy
• energy supplied = useful energy transferred + energy wasted
• efficiency(joules) = useful energy transferred by the device / total energy supplied to the device
• A system is an object or group of objects
• gravitational potential energy = mass x gravitational field strength ( roughly 9.81 N/kg) x height
• elastic potential energy = 1/2 x spring constant x extension ^2
• Internal energy - the total kinectic and potential energy of all the particles that make up a system
• Heating changes the energy stored in a system in a system by increasing the energy of the particles in it, which will either increase the temperature or cause a change of state
• Specific heat capacity - The amount of energy needed to raise the temperature of 1kg of a substance by 1 degree
• change in thermal energy = mass x specific heat capacity x change in temperature
• The higher the specific heat capacity of an object, the more energy is required to raise its temperature.
• Energy stores:

  • Kinetic
  • Thermal
  • Chemical
  • Gravitational Potential
  • Elastic Potential
  • Nuclear
• Energy Transfers:

  • Waves
  • Heating
  • Force
  • Electricity