Energy Stores

• Energy stores


  • Kinetic
  • Gravitational
  • Elastic
  • Magnetic
  • Electrostatic
  • Chemical
  • Nuclear
  • Thermal
• Kinetic energy


  Energy of moving objects
• Gravitational potential energy


  Energy of objects when lifted through a gravitational field
• Elastic potential energy


  Energy of objects when stretched, squashed or bent
• Magnetic energy


  Energy of magnetic materials interacting with each other
• Electrostatic energy


  Energy of objects with charge interacting with one another
• Chemical energy


  Energy transferred during chemical reactions
• Nuclear energy


  Energy released from atomic nuclei during nuclear reactions
• Thermal energy


  Energy of all objects, the hotter the object the more energy it has
• Kinetic Energy


  Energy in the kinetic store is defined as the amount of energy an object has as a result of its mass and speed
• If an object speeds up


  Energy is transferred to its kinetic store
• If an object slows down


  Energy is transferred away from its kinetic store
• Kinetic energy equation


  Ek = ½ × m × v2
• Kinetic energy equation variables


  • Ek = kinetic energy in joules (J)
  • m = mass of the object in kilograms (kg)
  • v = speed of the object in metres per second (m/s)
• Gravitational Potential Energy


  • The energy an object has due to its height in a gravitational field
• Gravitational Potential Energy changes


  1. If an object is lifted up, energy is transferred to its gravitational potential store

  2. If an object falls, energy will be transferred away from its gravitational potential store
• Gravitational Field Strength


  • The gravitational field strength (g) on the Earth is approximately 9.8 N/kg
  • The gravitational field strength on the surface of the Moon is less than on the Earth
  • The gravitational field strength on the surface of the gas giants (eg. Jupiter and Saturn) is more than on the Earth
• Elastic Potential Energy


  Energy in the elastic potential store of an object
• Elastic Potential Energy


  • The energy stored in an elastic object when work is done on the object
  • Any object that can change shape by stretching, bending or compressing (eg. springs, rubber bands)
• Storing energy in a spring's elastic potential store


  1. Spring is stretched (or compressed)

  2. Work is done on the spring

  3. Energy is transferred to the elastic potential store of the spring
• Releasing energy from a spring's elastic potential store


  1. Spring is released

  2. Energy is transferred away from its elastic potential store
• Extension, e, of a stretched spring


  How to determine the extension of a stretched spring
• The above elastic potential energy equation assumes that the spring has not been stretched beyond its limit of proportionality
• Thermal Energy


  Energy in the thermal store of an object responsible for its temperature
• Specific heat capacity


  The amount of energy required to raise the temperature of 1 kg of a substance by 1 °C
• Substances with low specific heat capacity


  • Heat up and cool down quickly
  • It takes less energy to change their temperature
• Substances with high specific heat capacity


  • Heat up and cool down slowly
  • It takes more energy to change their temperature
• Specific heat capacity


  Determines how useful a substance would be for a specific purpose