THE ABILITY TO CAUSE CHANGE 1

mechanical energy T y p e s o f E n e r g y 2

types of energy oToThermal energy - due to temperature (recall that this comes from the motion of molecules, so it is really kinetic energy) oHoHeat energy -transfer of thermal energy oCoChemical Potential Energy - stored in chemical bonds oNoNuclear energy - stored in the nuclei of an atom oEoElectrical energy - EM interactions oRoRadiant energy -carried by EM waves 3

Energy Energy is the capacity (ability) to do work. Kinetic Energy: Associated with an object in motion Potential Energy: Present in an object that has the potential to move because of its position 4 CLIP

Kinetic Energy MotionMotion KE of an object depends upon two variables:KE of an object depends upon two variables: 1.the mass (m) of the object 2.the speed (v) of the object. 5

A formula to find the kinetic energy of any body based on its velocity. Calculating Kinetic Energy 6

Potential Energy An object can store energy as the result of its position.An object can store energy as the result of its position. 7

Forms of potential energy -position above the Earth’s surface -stored in something stretchy -chemical reaction 8

Gravitational Potential Energy GPE is the energy stored in an object as the result of its vertical position (i.e., height). Amt. of GPE is dependent on two variables: 1.the mass 2.the height 9

Calculating Gravitational Potential Energy 10

Elastic Potential Elastic PE is the energy stored in elastic materials as the result of their stretching or compressing. 11

12 Conservation of Energy

Conservation of EnergyEnergy cannot be created or destroyed…only changed from one form to another. The total energy of an isolated system remains constant (isolated systems have no external forces and no mass changes) 1313

1414 ENERGY BEFORE = ENERGY AFTER Energy can be changed from one form to another, but it does not disappear.

Mechanical Energy The motion of some objects contain a combination of only kinetic and potential energies. ME is the sum of the KE and forms PE associated with a system Therefore, ME= KE + PE 15

TOTAL ENERGY OF THE SYSTEM REMAINS THE SAME Conservation of Energy 1616

Conservation of Energy TOTAL ENERGY OF THE SYSTEM REMAINS THE SAME 1717

Conservation of Mechanical Energy: Therefore, ME i = ME f KE i + PE i = KE f + PE f ½ mv i 2 + mgh i = ½ mv f 2 + mgh f 1818

Conservation of Mechanical Energy: Conservation of ME only hold true when the only energies of the system are KE and PE. Therefore, in the presence of friction energy is transformed to other types of energies. 19

Energy Conversion When one type of energy is changed or transformed into another type of energy 20

Can you think of More? Create a graphic organizer to illustrate energy conversions. draw a picture to represent four different energy conversion you may encounter in everyday life. Be sure to explain what type of energy it starts with and what type of energy it ends with. Examples 2121 Battery Lighting a Match Steam Engine

Energy Conversion clip 22

What about a falling object? What happens when it hits the ground? Where did the energy all go? 23

As it is falling and when the object hits the ground the energy is converted into other types of energy such as: Energy Conversions of a dropped object If the object bounces, some energy is converted momentarily into elastic potential energy. sound energy (waves), Light Energy (sparks), thermal energy due to friction (heat) in the ground and air, vibrations in the earth (energy waves.) 24

If Robin Hood had been Written by an Engineer.... And Robin didst slowly and with great determination put potential energy equal to the work of his muscles into an elastic storage device. And therewith Robin the Bold and Valiant didst convert this stored energy most quickly, efficiently, and accurately into the velocity of a sturdy and pointed dart (oft called arrow) such that almost all of its former potential energy didst become kinetic. Then this speedy dart didst split an arrow (oft called dart) already buried in most distant target, having been previously hurled there at an equally great speed by a similar conversion of stored energy. 25

EOCT Questions Which statement about energy is true? A Energy can be increased in a closed system. B Energy cannot be conserved. C Energy can be decreased in a closed system. D Energy cannot be created nor destroyed.