Topic One - Energy

• what is a system?

  an object or group of objects
• what are the different types of systems?

  a closed system and an open system
• what can open systems do?

  they can exchange energy and matter with their surroundings
• what does a closed system do?

  they don't let energy or matter in or out eg. a thermos
• whats the measure of energy?

  joules
• what is the conservation of energy?

  energy cannot be created or destroyed, only transferred or transformed from one store to another
• how many energy stores are there?

  8
• how is energy stored in the thermal store?

  stored as heat in objects
• how is energy stored in the chemical store?

  stored in chemical bombs eg. batteries, food, fuel
• how is energy stored in the GPE store?

  stored in objects lifted against gravity
• how is energy stored in the kinetic store?

  stored in objects that move
• how is energy stored in the elastic potential store?

  stored in stretched or squashed objects
• how is energy stored in the electrostatic store?

  stored as electrical charge
• how is energy stored in the magnetic store?

  stores between objects in a magnetic field
• how is energy stored in the nuclear store?

  stored within atoms
• energy can move between the stored through different pathways
• what are the four energy pathways?

  heating, electrical, radiation, mechanically
• thermal energy is transferred through the heating energy pathway
• in the electrical energy pathway, energy is transferred from an electrical power source
• in the radiation energy pathway, energy is transferred through light and sound
• the mechanical energy pathway is when a force acts on an object
• energy dissipation occurs when energy (usually thermal) spreads out into its surroundings
• an example of an energy transfer would be a person throwing up a ball (chemical ---> kinetic, mechanically)
• another example of energy transfer is a kettle boiling [thermal (heating element) ---> thermal (water), by heating]
• what is the equation for kinetic energy?

  $\ 1/2mv^2$ [kinetic energy(J) = 0.5 x mass (kg) x velocity squared (m/s)]
• what is the equation for GPE?


  $\ mgh$[gpe (J) = mass (kg) x gravitational field strength (N/kg) x height (m)]
• with kinetic energy, more mass or higher velocity will equal more energy
• with gpe, greater height will equal greater energy
• whats the equation for elastic potential?

  $\ 1/2ke^2$[elastic potential (J) = 0.5 x spring constant (N/m) x extension squared (m) ]
• what is spring constant?

  spring constant is the stiffness of a spring --> it informs how much force is required to stretch in by 1m
• in elastic potential, a greater extension will lead to greater energy
• what is an extension?

  an extension (e) is how much the object is stretched or compressed, measured in metres
• what is the equation to figure out spring constant?

  force divided by extension
• whenever you heat up or cool down an object, there is a change in energy
• the amount of energy stored or released from a system as its temperature changes can be calculated by knowing the specific heat capacity
• what is specific heat capacity (SHC) ?

  amount of energy required to raise the temperature of a substance weighting 1kg by 1 degree
• what is the formula for calculation the change in thermal energy?

  Q = mcΔT [ m is the mass of the substance ( kg) , c is the specific heat capacity of the substance (J/kg *C), and ΔT is the change in temperature (*C)]
• what is power?

  power is the rate at which work is done, the amount of energy transferred each second
• what are the equations for power? 


  power (w) = energy transferred (J) divided by time (s) power (w) = work down (J) divided by time (s)
• power is measured in watts:

  a watt is the same as saying 1 joule of energy transferred per second (1 J/s)