Energy Chapter 4

What is energy? The ability to cause change Moving baseball had energy Caused the window to change Need energy to yawn, open a book or write with a pen…

Different Forms of Energy Electrical Chemical Radiant Thermal

Kinetic Energy Energy in motion Depends on object’s mass and speed Measured in joules Formula KE=1/2(m)(v2) Unit= Joules (J)

Potential Energy Stored energy Potential to cause change Amount due to position Types: Elastic PE- stored by something that can stretch Chemical PE- stored in chemical bonds Gravitational PE- stored by anything that can fall - based on mass and height

Transforming Energy Light bulb: electrical to light & thermal energy Gasoline: electric spark ignites gas molecule producing thermal energy, gases expand and move parts of car = mechanical kinetic energy Others?

Conversions between PE & KE Mechanical energy is the total amount of KE and PE in a system

The Law of Conservation of Energy Energy cannot be created or destroyed only transferred Total amount of energy in the universe does not change Electrical energy = Thermal energy Kinetic energy Sound energy

Here comes Mr. Friction again! Swinging on a swing, you will eventually come to a stop… did the KE just disappear? No! Some energy transferred back to PE and some was changed to heat by friction… the swing’s chains rub on the hooks and air rushes past the swinger  thermal energy! Amount of total energy is still the same

Mass to Energy Special kind of energy conversions Nuclear Fusion: combining atoms to transform mass into energy  SUN!! Nuclear Fission: atomic nuclei are split to transform mass into energy  uranium

Torque a measure of how much a force acting on an object causes that object to rotate object rotates about an axis T = Force x distance

Force distance