Energy Conversion and Conservation Chapter 15.2

Energy Conversion Energy can be converted from one form to another ElectricalThermalElectromagnetic ChemicalMechanical Thermal

Striking a Match Muscles use chemical energy to move your hand to strike the match Friction between match and box converts some of match’s kinetic energy into thermal energy Thermal energy triggers a chemical reaction releasing chemical energy Stored chemical energy is converted into thermal energy and electromagnetic energy

Conservation of Energy Law of Conservation of Energy = energy cannot be created or destroyed Energy can only be converted from one form to another The amount of energy at the beginning of a process is the same as the amount of energy at the end.

Riding a bike… Stop pedaling, the bike will eventually come to a stop. Where did the bike’s kinetic energy go? FRICTION! The work done by friction changes kinetic energy into thermal energy As the bike slows, it gains thermal energy. (So do the ground and air)…energy is conserved overall

Energy Conversions The gravitational potential energy of an object is converted to the kinetic energy of motion as the object falls. Conversions between kinetic and potential energy can happen in both directions KINETICPOTENTIAL

conservation of energy by Walter Lewin

Pendulum PE = max KE = 0 PE = max KE = 0 PE = 0 KE = max

Pendulum

Conservation of Mechanical Energy

Gravitational PE at beginning? 0 0

Energy and Mass