Physics- Energy transfers

• Conservation of energy


  Energy can be transferred usefully, stored or dissipated, but it cannot be created or destroyed
• Energy transfer within a system

  1. Gravitational potential energy at the top

  2. Kinetic energy at the bottom

  3. Gravitational potential energy as it swings back up
• Friction in the system

  Causes energy to be transferred to thermal energy stores
• Dissipated energy


  Energy that is wasted and less useful
• Reducing friction can reduce unwanted energy transfers
• Lubricant such as oil can reduce friction in the pendulum system
• Removing air particles from around the pendulum can reduce friction
• Energy transfers in a pendulum swing

  Gravitational potential energy is transferred to kinetic energy and then vice versa
• Energy transfers in a bungee jump

  1. At the start, all energy is in the gravitational potential energy store

  2. As the jumper falls, energy is transferred from gravitational potential energy store to kinetic energy store

  3. When the bungee rope starts to tighten, the kinetic energy store is at its maximum

  4. When the rope is fully extended, the kinetic energy store is zero and all energy is in the elastic potential energy store

  5. As the bungee rope recoils, energy is transferred from the elastic potential energy store back to the kinetic energy store

  6. During the ascent, energy transfers from the kinetic energy store back to the gravitational potential energy store

  7. At the top of the ascent, all energy is in the gravitational potential energy store
• The jumper never returns back to the original position
• Energy is dissipated as thermal energy


  • Due to friction with air particles as the jumper passes through the air
  • Due to stretching effects in the bungee rope (bungee ropes are not fully elastic)