Work and Energy

• What is the principle regarding energy in physics?

  Energy is never created or destroyed; it is only transferred between different forms and objects.
• What are the different forms of energy mentioned in the video?

  • Thermal or internal energy
  • Kinetic energy
  • Gravitational potential energy
  • Elastic potential energy
  • Chemical energy
  • Magnetic energy
  • Electrostatic energy
  • Nuclear energy
• What is thermal or internal energy related to?

  It is related to the heat energy trapped within an object and its temperature.
• What is kinetic energy associated with?

  Kinetic energy is associated with the movement or motion of an object.
• What does gravitational potential energy depend on?

  It depends on the position of an object in a gravitational field.
• What is elastic potential energy?

  Elastic potential energy is the energy held in an already stretched spring.
• What is chemical energy?

  Chemical energy is held in chemical bonds.
• What is magnetic energy?

  Magnetic energy is what holds magnets to your fridge.
• What is electrostatic energy?

  Electrostatic energy is what occasionally gives you a shock when you touch your car.
• What is nuclear energy?

  Nuclear energy is what we get from breaking atoms apart.
• How can energy be transferred between different forms?

  Energy can be transferred mechanically, electrically, by heating, or by radiation.
• What is a system in physics?

  A system is a collection of matter that we consider for energy transfer analysis.
• What happens in an open system?

  In an open system, matter can exchange energy with the outside world.
• What is a closed system?

  A closed system is separate from the outside world, so neither matter nor energy can enter or leave.
• What happens to energy in a closed system?

  The overall change in energy is always zero, even though energy can be transferred within the system.
• How does energy transfer occur when boiling water in a kettle?

  1. Electrical energy flows from the plug socket to the kettle's heating element.
  2. This energy is transferred to the thermal energy store of the heating element.
  3. The heating element then transfers energy to the water's thermal energy store.
• What is another term for energy transferred?

  Work done.
• What are the two main types of work done?

  Mechanical work and electrical work.
• What is an example of mechanical work done?

  Kicking a ball up in the air.
• What is electrical work done?

  Electrical work is done when current flows and energy is required to overcome resistance in wires.
• How does friction do work on a train that is stopping?

  Friction slows the train down by transferring energy from the wheels' kinetic energy stores to the thermal energy stores of the surroundings.
• What are the key differences between open and closed systems?

  Open System:

  • Can exchange energy and matter with the outside world.
  • Can gain or lose energy.

  
  

  Closed System:

  • Is separate from the outside world.
  • Cannot exchange matter or energy.
  • Overall energy change is zero.
• What is the focus of today's video?

  Understanding and calculating power
• How many definitions of power are there?

  Two definitions
• What is the first definition of power?

  Rate at which energy is transferred
• What is the equation for power based on energy transferred?

  Power = Energy transferred / Time
• What is the equation for power based on work done?

  Power = Work done / Time
• What is the second definition of power?

  Rate at which work is done
• What does "work done" refer to?

  Energy transferred using a force
• If you push a car down the road, what is the energy referred to as?

  Work done
• How is electrical energy transferred from a plug socket to a phone referred to?

  Energy transferred
• In what unit is power measured?

  Watts
• In what unit is energy transferred measured?

  Joules
• In what unit is work done measured?

  Joules
• In what unit is time measured?

  Seconds
• How do you calculate the power of the left lamp transferring 1200 joules over 20 seconds?

  Power = 1200 J / 20 s = 60 W
• How do you compare the power of two lamps?

  • Use the energy transferred version of power equation
  • Calculate power for each lamp
  • Compare the results
• How do you calculate the power of the right lamp transferring 1500 joules over 30 seconds?

  Power = 1500 J / 30 s = 50 W
• Which lamp is more powerful based on the calculations?

  The left lamp
• How do you find the energy transferred by an 1100 watt microwave running for three minutes?

  Energy = Power × Time