 Energy is the ability to do work or cause change.  When work is done energy is transferred to the object.  The unit for energy is the JOULE

Kinetic Energy Potential Energy GravitationalElastic DefinitionThe energy of motion Stored energy due to the object’s height Stored energy due to the object’s shape Factors that affect the energy The object’s mass and velocity (speed) The object’s weight and its height above the ground How much the object is stretched or compressed Formula and Magic Triangle KE = ½ MV 2 PE = MGH MG = Weight You will not be asked to calculate this. EPE = ½ KX 2

 Associated with the position and motion of an object.  A combination of an object’s PE and KE (total energy of the object at any one time)  An object with ME can do work on another object.  ME = the ability to do work  The more ME, the more work an object can do

 ME = PE + KE  Sometimes an object’s ME is just its potential energy and sometimes it is just its kinetic energy.

 ME = PE + KE  ME = 32J + 45J  ME = 77J

 Question: If an object’s mechanical energy is equal to its potential energy, how much kinetic energy does it have? o The object has 0 J of kinetic energy. byss.uoregon.edu

 The total kinetic and potential energy of the ATOMS in an object is its thermal energy.

 Friction turns mechanical energy into thermal energy  Energy “lost” due to friction still exists – it is now the energy of heat!  Other examples: melting, heating, freezing, lava…

 Doubling the velocity has a greater impact on the kinetic energy because when calculating KE the velocity is squared.  Doubling the velocity will result in quadrupling the energy. Doubling the mass only doubles the energy.

 A skier would have a greater GPE on a higher ski jump because that person’s height above the Earth’s surface is greater. The higher the height the higher the GPE (GPE = weight x height)

 While holding it back it has lots of potential to move the arrow in the tension of the bow. This is elastic potential energy because the bow can stretch.

 The energy of the bow is transformed into kinetic energy and then transferred to the arrow almost instantly causing both the bow string and arrow to accelerate forward.

 You need to know the sky diver’s weight (mass x gravity) and height above the Earth’s surface (altitude).  Use the equation:  GPE = MGH  GPE = mass (kg) x 9.8 x height (m)

 You need to know the sky diver’s mass and velocity.  Use the equation: KE = ½ mv 2  KE = ½ mass (kg) x velocity 2 (m/s) 2

 The apple’s mechanical energy is 8.7 J (5.2 J J) since  ME = KE + PE.

 Friction turns mechanical energy into thermal energy  During friction 2 surfaces rub against each other – this produces heat!  Energy “lost” due to friction still exists – it is now the energy of heat!  The total kinetic and potential energy of the ATOMS in an object is its thermal energy.