energy

• What is a system in physics?

  An object or group of objects
• How does energy storage change in a system?

  It changes when the system changes
• What happens to kinetic energy when a ball hits a wall?

  • Kinetic energy is transferred as sound
  • The system is the moving ball
• What occurs to a vehicle's kinetic energy when it slows down?

  • Kinetic energy transfers to thermal energy
  • This occurs due to friction between wheels and brakes
• What is the formula for kinetic energy?

  $E_k =$$\frac{1}{2}mv^2$
• What do the variables in the kinetic energy formula represent?

  m is mass, v is speed, E_k is energy
• What type of energy is stored in a stretched spring?

  Elastic potential energy
• What is the formula for elastic potential energy?

  $E_e =$$\frac{1}{2}ke^2$
• What do the variables in the elastic potential energy formula represent?

  E_e is energy, k is spring constant, e is extension
• What is the formula for gravitational potential energy?

  $E_p =$$mgh$
• What do the variables in the gravitational potential energy formula represent?

  E_p is energy, m is mass, g is gravitational field strength, h is height
• What is specific heat capacity?

  Energy to raise 1kg by 1°C
• What is the formula for calculating thermal energy change?

  $E =$$mc\Delta T$
• What do the variables in the thermal energy change formula represent?

  E is energy, m is mass, c is specific heat capacity, ΔT is temperature change
• How is power defined in physics?

  Rate at which energy is transferred
• What is the formula for power?

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

  1 watt of power
• How can you determine which motor is more powerful?

  The one that does work faster
• What are the ways energy can be transferred?

  • Usefully
  • Stored
  • Dissipated
  • Cannot be created or destroyed
• What is energy dissipation in systems?

  • Energy is stored in less useful ways
  • Often described as 'wasted' energy
• How can energy waste be reduced?

  • Lubrication reduces friction
  • Thermal insulation minimizes heat loss
• What is thermal conductivity?

  Rate at which heat travels through a material
• How does thermal conductivity affect energy transfer in buildings?

  Higher conductivity allows faster heat transfer
• What happens to heat loss with thick, low conductivity walls?

  Rate of cooling is low
• What happens with thin metal walls regarding heat loss?

  Heat is lost very quickly
• How is efficiency defined?

  Ratio of useful work to energy supplied
• What is the formula for efficiency?

  $\text{efficiency} =$$\frac{\text{useful energy output}}{\text{total energy input}}$
• How can efficiency be increased in a system?

  • Reducing waste output
  • Recycling waste output
• What are the main non-renewable energy sources?

  Fossil fuels and nuclear fuel
• What are the main renewable energy sources?

  Biofuel, wind, hydro-electricity, geothermal, tidal, solar, water waves
• What is renewable energy?

  Energy that can be replenished as used
• Why is non-renewable energy used more for large-scale supplies?

  It provides large energy output per kilogram
• Why has renewable energy become more important recently?

  Finite lifetime of fossil fuels
• What are some reliability issues with renewable energy?

  Solar doesn't work at night; wind is intermittent
• What are the main uses of energy?

  • Transport
  • Electricity generation
  • Heating
• What are the environmental impacts of energy extraction?

  • Fossil fuels destroy landscapes
  • Wind turbines can be eyesores
• What are the environmental impacts of using energy sources?

  • Fossil fuels release harmful emissions
  • Solar and wind have no emissions
• What patterns and trends have emerged in energy use?

  • Fossil fuels became important during the industrial revolution
  • Renewable energy has become more suitable recently
  • Increased public power demands complicate environmental issues