Energy

• What is a system in physics?

  An object or group of objects
• What happens to energy storage when a system changes?

  There are changes in energy storage
• What are common situations where energy storage changes?

  • An object projected upwards
  • A moving object hitting an obstacle
  • An object accelerated by a constant force
  • A vehicle slowing down
  • Bringing water to a boil in an electric kettle
• How can students calculate changes in energy?

  energy change = energy in - energy out.
• What is the equation for kinetic energy?

  $E_k =$$0.5 \times m \times v^2$
• What do the variables in the kinetic energy equation represent?

  Ek is energy, m is mass, v is speed
• What is the equation for elastic potential energy?

  $E_e =$$0.5 \times k \times e^2$
• What do the variables in the elastic potential energy equation represent?

  Ee is energy, k is spring constant, e is extension
• What is the equation for gravitational potential energy?

  $E_p =$$m \times g \times h$
• What do the variables in the gravitational potential energy equation represent?

  Ep is energy, m is mass, g is gravitational field strength, h is height
• How is the change in thermal energy calculated?

  $\Delta E =$$m \times c \times \Delta \theta$
• What does specific heat capacity measure?

  Energy needed to raise 1 kg by 1°C
• What is the definition of power in physics?

  • Rate at which energy is transferred
  • Rate at which work is done
• What is the equation for power?

  $P =$$\frac{E}{t}$
• What does an energy transfer of 1 joule per second equal?

  1 watt of power
• What are the three types of energy transfers in a closed system?

  • conduction, convection, and radiation,
• What happens to energy in a closed system?

  No net change to total energy
• How can unwanted energy transfers be reduced?

  Through lubrication and thermal insulation
• What affects the rate of cooling in buildings?

  Thickness and thermal conductivity of walls
• What is the equation for efficiency?

  $Efficiency =$$\frac{useful \ output \ energy}{total \ input \ energy}$
• How can efficiency be expressed?

  As a decimal or percentage
• What are the main energy resources available on Earth?

  • Fossil fuels (coal, oil, gas)
  • Nuclear fuel
  • Bio-fuel
  • Wind
  • Hydro-electricity
  • Geothermal
  • Tides
  • Sun
  • Water waves
• What is a renewable energy resource?

  One that can be replenished as used
• What are the uses of energy resources?

  Transport, electricity generation, and heating
• How can students distinguish between renewable and non-renewable resources?

  By identifying their replenishment ability
• Why are some energy resources more reliable than others?

  Due to their availability and consistency
• What environmental impacts arise from energy resource use?

  Pollution, habitat destruction, and resource depletion
• What is the role of science in identifying environmental issues?

  Identifies issues but lacks power to resolve
• What is the main power source for portable devices?

  Batteries of some kind
• What did 19th-century scientists contribute to electricity?

  Fundamentals of electromagnetism
• What is a limitation of power stations?

  They have a limited lifetime