Energy

Is defined as the Ability to do Work Energy has Two Types: Kinetic (Energy of Motion) and Potential (Stored Energy)

Kinetic Energy KE = ½ m v 2 Ex: A moving car has the ability to do work on the light pole if it hits it.

Potential Energy 2 possibilities Gravitational PE - Object lifted to some height Elastic PE - A stretched or compressed object (spring or rubber band)

Gravitational Potential Energy or Wi ll it fall? GPE = m g h m is the mass of the object in Kg, g is the acceleration due to gravity which is 9.8 m/s 2 on earth and h is the height in meters

Use the formula page! PE = mgh 41 What is the potential energy of the rock? A 59,900 joules B 64,600 joules C 93,100 joules D 121,600 joules m = 95 kg g = 9.8 m/s 2 h = 100 m 95 kg x 9.8 m/s 2 x 100 = 93,100 joules C

Law of Conservation of Energy Energy can change forms, but is never created nor destroyed Loss in one form = gain in an another form A falling object speeds up as it falls to the ground; PE decreases as KE increases. The KE it has at impact = the PE it had before it fell.

Example: A falling object speeds up as it falls to the ground; PE decreases as KE increases, the KE it has at impact with the ground is equal to the PE it had before it fell

Energy can be conserved in Non-Mechanical forms The chemical energy in a battery transforms into electrical energy Any reaction where more energy is given off than is used to start it is Exogonic An Endogonic reaction absorbs energy and causes cooling

Electrical Energy - Moving electrons in a path is electricity Electrical Potential Difference (v) is measured in Volts The rate of moving electric charges, Electric Current (I), is measured in Amperes Resistance or opposition to the movement of the energy is called Resistance (R).

Thermal Energy A body contains internal KE due to the motion of its atoms ( they are constantly wiggling and jiggling) Thermal Energy is the total internal KE of a body Temperature is the average KE of a body

Heat- Transfer of Thermal Energy 1. Conduction-direct contact, a pot heating on a stove (solids) 2. Convection- heating by circulating fluids, (gas and liquid) heating from a fireplace And... Three forms of heating:

3. Radiation – Transfer of Electromagnetic (E.M.) Energy Objects are heated when exposed to infrared radiation The suns heats the earth by sending infrared radiation along with other forms of E.M. energy 3.0 x 10 8 meters through empty space

Heat moves by conduction in solids since the particles are close together and vibrate Heat convection occurs in gases and liquids. Heat convection does not occur in solids because solids are unable to — A absorb heat by vibrating B transfer heat by fluid motion C emit radiation by reflecting light D exchange heat by direct contact Solids do radiate heat to their surroundings

2 The primary way liquids and gases transmit heat is by the process of — F reflection G conduction H radiation J convection Fluid heat movement is convection. Fluid motion occurs in liquids and gases.

F improve emission of infrared radiation G reduce the heat loss by convection currents H improve absorption of infrared radiation J reduce the heater’s conducting properties 50 A solar heater uses energy from the sun to heat water. The heater’s panel is painted black to — Emission is giving off – we want to absorb: Not F Convection is movement of heat in fluid matter, heat loss would be from a solid exterior – Not G Painting a substance will not change its conductivity – That is a property of metals. It would have to be made of a different substance to change that: Not J