BBC Bitesize - Physics Energy - Changes in Energy stores

What can and can’t be done with energy?

Energy can transferred but cannot be destroyed

What are examples of energy stores?

Magnetic energy , kinetic energy , gravitational potential energy, elastic potential energy, chemical energy etc…

What is the equation for kinetic energy?

Kinetic energy (Ek) (Joules (J) = ½ x mass x velocity²

What is the equation for gravitational potential energy?

Gravitational potential energy (Ep) (J) = mass (kg) x gravitational field strength (N/kg) x height (metres)

What is the equation for elastic potential energy?

elastic potential energy = ½ x force (N) x extension of the spring (m)

What is the other equation for elastic potential energy?

Elastic potential energy = ½ x spring constant (N/m) x spring extension (m)

= Ee = ½ke²

What is magnetic energy?

The energy stored when repelling poles have been pushed closer together or when attracting poles have been pulled further apart

What are examples of magnetic energy?

Fridge magnets, compasses, maglev trains which use magnetic levitation

What is thermal energy?

The total kinetic and potential energy of the particles in an object

What are examples of thermal energy?

* Human bodies, hot coffees, stoves or hobbs, Ice particles vibrate slowly but still have energy

What is chemical energy?

* The energy stored in chemical bonds such as those between molecules

What are examples of chemical energy?

* Foods, muscles and electrical cells

What is kinetic energy?

* The energy from a moving object

What are examples of kinetic energy?

* Runners, buses and comets

What is electrostatic energy?

• The energy stored when repelling charges have been moved closer or when attracting charges have been pulled apart

What are examples of electrostatic energy?

* Thunderclouds, Van de Graaf generators

What is elastic potential energy?

* The energy stored when an object is stretched or squashed

What are examples of elastic potential energy?

* Drawn Catapults, compressed springs, inflated balloons

What is gravitational potential energy?

* The energy of an object at a height

What are examples of gravitational potential energy?

* Aeroplanes and kites

What is nuclear energy?

* The energy stored in the nucleus of an atom

What is an example of nuclear energy?

* Uranium nuclear power, nuclear reactors

What is an energy transfer?

When energy changes from one type to another

e.g chemical energy --→ kinetic energy

What are examples of energy transfers?

* Boat being accelerated by the force of the engine

(chemical energy → kinetic energy)
* Swinging pirate ship ride at a theme park

(kinetic energy to gravitational potential energy)

How can energy be transferred?

* mechanical work - a force moving an object through a distance
* electrical work - changes moving due to potential difference
* heating - due to temperature difference caused by electricity or chemical reactions
* radiation - energy transferred as a wave e.g light and infared radiation are emitted from the sun

What is dissipation?

* When energy is wasted and let out into the atmosphere

How is energy dissipated in a mechanical system?

* In a mechanical system, energy is dissipated when two surfaces rub together

How is energy wasted in a mechanical system

* Work is done against friction which causes heating of the two surfaces - so the internal (thermal) energy of the surface increases

How can energy be preserved in a mechanical system?

* In a mechanical system, energy is preserved by adding a lubricant between the surfaces. This reduces friction and so less energy is wasted