Physics

• What is a system?

  An object or group of objects
• What happens when something changes in a system?

  Energy is transferred between its stores and the surroundings
• What is a closed system?

  A system where no energy can be transferred and the total energy does not change
• What is kinetic energy?

  Energy a moving object has
• What is gravitational potential energy?

  The energy an object has because of its height above the ground
• What is elastic potential energy?

  The energy an elastic object has when it is stretched or compressed
• What is thermal energy?

  Energy an object has because of its temperature
• What is chemical energy?

  The energy that can be transferred by chemical reactions
• What is nuclear energy?

  The energy stored in the nucleus of an atom
• What is magnetic energy?

  The energy a magnetic object has when it is near a magnet or in a magnetic field
• What is electrostatic energy?

  The energy a charged object has when near another charged object
• What are the energy stores?

  • Kinetic
  • Gravitational potential
  • Elastic potential
  • Thermal
  • Chemical
  • Nuclear
  • Magnetic
  • Electrostatic
• What are energy transfers?

  The ways in which energy can be transferred to and from different stores
• What are the different types of energy transfer?

  • Heating
  • Waves
  • Electricity
  • Forces (mechanical work)
• What is heating (in terms of energy transfers)?

  When energy is transferred from one object to another with a lower temperature
• What are waves (in terms of energy transfers)?

  When waves such as light and sound can transfer energy
• What is electricity (in terms of energy transfers)?

  When an electric current transfers energy
• What are forces (in terms of energy transfers)?

  When energy is transferred when a force moves or changes the shape of an object
• What is work done?

  The energy transferred when a force moves an object
• What is the unit for energy?

  Joules (J)
• What is one joule of work?

  The work done when a force of 1N causes an object to move 1m in the direction of the force
• Describe the energy transfer when a moving car slows down?

  Energy is transferred mechanically from the kinetic store of the car to the thermal store of the brakes. Some energy is dissipated to the thermal store of the surroundings.
• What unit represents one joule transferred per second?

  Watt (W)
• What is power?

  How much work is done or how much energy is transferred per second
• What is the unit of power?

  Watt (W)
• What is lubrication?

  A way of reducing unwanted energy transfer due to friction
• What is streamlining?

  A way of reducing energy wasted due to air resistance
• What is thermal insulation?

  A way of reducing energy wasted due to heat dissipated into the surroundings
• What is efficiency?

  A measure of how much energy is usefully transferred
• What does a material’s thermal conductivity tell you?

  How well it conducts heat
• Which materials have low thermal conductivity?

  Thermal insulators
• What are three factors that affect the rate of thermal energy transfer?

  • Thermal conductivity of material
  • Temperature difference
  • Thickness of material
• What factors affect the rate of heat loss from a building?

  • Thickness of walls and roof
  • Thermal conductivity of walls and roof
  • Temperature difference between the inside and outside
• What is specific heat capacity?

  The amount of energy needed to raise the temperature of 1 kg of a material by 1 °C
• What is infrared radiation?

  A type of electromagnetic radiation
• What is the relationship between the temperature of an object and its emission of infrared radiation?

  The higher the temperature of an object, the more infrared radiation emitted - it is directly proportional
• What is true about an object that absorbs and emits infrared radiation at the same rate?

  It is at a constant temperature
• What is a black body?

  A theoretical object that absorbs 100% of the radiation that falls on it, does not reflect or transmit any radiation, and is the best emitter of radiation
• What are three greenhouse gases?

  • Methane
  • Water vapour
  • Carbon dioxide
• Why do greenhouse gases affect the Earth's temperature?

  The Earth’s surface absorbs and re‑emits radiation from the Sun, which greenhouse gases absorb – they re‑emit this radiation back towards Earth’s surface, so the radiation never leaves the atmosphere