Conservation & Dissipation of Energy

state the conservation of energy

Energy cannot be created or destroyed, it can only be transferred from one store to another

so what does the conservation of energy mean (3)

• This means the total amount of energy in a closed systemremains constant 

• Energy can be transferred from store to store usefully (to do work)

• Or energy can be dissipated to the thermal store of the surroundings

describe the energy transfer that occurs when a bat hits a ball (5)

• The moving bat has energy in its kinetic store

• Some of that energy is transferred usefully to the kineticstore of the ball

• Some of that energy is dissipated  by heating to the thermal store of the bat, the ball, and the surroundings

  • The impact of the bat and the ball causes the particles of the bat and ball to vibrate 

  • The sound wave causes the air particles to vibrate

describe the energy transfer that occurs in an electric heater (3)

• Energy is transferred electrically from the mains supply to the thermal store of the heating element

• Some of that energy is usefully transferred to the thermal store of the surroundings by heating the air particles in the room

• Some of that energy is dissipated to the thermal store of the surroundings by radiation (light)

describe the energy transfer that occurs on a rollercoaster? (7)

• When the rollercoaster is on an elevated piece of track, it has energy in its gravitational potential store

• When the rollercoaster descends to a lower piece of track, energy is transferred usefully to the kinetic store as the rollercoaster gains speed

• When the rollercoaster ascends again, energy is transferred from the kinetic store to the gravitational store as the rollercoaster loses speed

• Energy is dissipated to the thermal store of the surroundings by heating due to 

  • friction heating the wheels and track

  • sound waves vibrating the air particles

  • As the rollercoaster in the diagram travels from A to D, the useful energy transfers that take place are:

  gravitational potential store → kinetic store → gravitational potential store → kinetic store

  • This is sometimes also described as

  GPE → KE → GPE → KE

  
  

describe the energy transfer that occurs on a trampoline? (7)

• Whilst jumping, the person has energy in their kinetic store

• When the person lands on the trampoline, most of that energy is transferred to the elastic potential store of the trampoline

• That energy is transferred usefully back to the person'skinetic store as they bounce upwards

• Energy is transferred from the person's kinetic store to their gravitational potential store as they gain height 

• Some of the energy is dissipated by heating to the thermal store of the surroundings (the person, the trampoline and the air)

• The useful energy transfers taking place are:

elastic potential store → kinetic store → gravitational potential store

Describe the energy transfers in a falling object (1)

Energy is transferred mechanically from the gravitational potential store of the object to the kinetic store of the object

Describe the energy transfers in a battery powering a torch (1)

Energy is transferred electrically from the chemical store of the cell to the thermal store of the bulb

Describe the energy transfers for a mass on a spring (1)

Energy is transferred mechanically from the elastic potential store of the spring to the kinetic store of the mass