Energ stor&sys,k&p energy,shc,conservation of energy & power

• What happens to energy when it is transferred between different energy stores?

  Energy is never used up; it is just transferred between different energy stores and objects.
• What occurs when energy is transferred to an object?

  The energy is stored in one of the object's energy stores.
• What are the three common energy stores mentioned?

  • Kinetic energy store
  • Gravitational potential energy store
  • Elastic potential energy store
• How does movement relate to an object's kinetic energy store?


  Anything that is moving has energy in its kinetic energy store.
• What factors affect the energy in an object's kinetic energy store?

  The energy depends on the object's mass and speed.
• What is the formula for calculating kinetic energy?

  $E_k =$$\frac{1}{2}mv^2$
• Calculate the kinetic energy of a car with a mass of 2500 kg traveling at 20 m/s.

  $E_k =$$\frac{1}{2} \times 2500 \times 20^2 =$$500,000 \text{ J}$
• What happens when an object is lifted in a gravitational field?

  Work is done, causing a transfer of energy to the gravitational potential energy store.
• How does the height of an object affect its gravitational potential energy store?

  The higher the object is lifted, the more energy is transferred to this store.
• What factors determine the energy in a gravitational potential energy store?

  The energy depends on the object's mass and the strength of the gravitational field.
• What is the formula for calculating gravitational potential energy?

  $E_p =$$mgh$
• What happens to energy when an object falls?

  Energy from its gravitational potential energy store is transferred to its kinetic energy store.
• What effect does air resistance have on falling objects?

  Air resistance causes energy to be lost from the gravitational potential energy store.
• How is energy transferred when stretching or squashing an object?

  Energy is transferred to its elastic potential energy store.
• What is the formula for calculating elastic potential energy?

  $E_e =$$\frac{1}{2}ke^2$
• What is specific heat capacity?

  • It is the amount of energy needed to raise the temperature of 1 kg of a substance by 1 °C.
  • Different materials have different specific heat capacities.
• How much energy is needed to warm 1 kg of water by 1 °C?

  4200 J
• What is the equation that links energy transferred to specific heat capacity?

  ^E= mc^0
• What is the procedure to investigate specific heat capacities of solids?

  1. Measure the mass of the block.
  2. Wrap it in an insulating layer.
  3. Insert thermometer and heater.
  4. Measure initial temperature and set power supply.
  5. Record temperature and current every minute.
  6. Calculate power and energy transferred.
  7. Plot graph of energy transferred against temperature.
  8. Find gradient to determine specific heat capacity.
• What is the conservation of energy principle?

  Energy can be transferred, stored, or dissipated, but can never be created or destroyed.
• What happens to energy during transfers?

  Not all energy is transferred usefully; some is always dissipated.
• What is dissipated energy?

  Dissipated energy is energy stored in a way that is not useful, often as thermal energy.
• How does a mobile phone illustrate energy transfer?

  Energy is transferred from the chemical energy store of the battery, but some is dissipated as thermal energy.
• What occurs in a closed system?

  Energy transfers occur within the system, but no energy leaves the system, resulting in a net change of zero.
• What is power defined as?

  Power is the rate of energy transfer or the rate of doing work.
• How is power measured?

  Power is measured in watts.
• What is the relationship between watts and joules?

  One watt equals one joule of energy transferred per second.
• What is the formula for calculating power based on energy transferred?

  $P =$$\frac{E}{t}$
• What is the formula for calculating power based on work done?

  $P =$$\frac{W}{t}$
• How does the power of a machine relate to its energy transfer?

  A machine transfers a lot of energy in a short time, making it more powerful.
• Calculate the power of a motor that lifts a stunt performer with 8000 J of work in 50 seconds.

  $P =$$\frac{8000}{50} =$$160 \text{ W}$
• What happens to energy when it is wasted?

  When energy is wasted, it is not destroyed; it still exists but is not used efficiently.
• How much energy does a motor transfer if it transfers 4.8 kJ in 2 minutes?

  1. 8 kJ