Energy

Energy

Is defined as the Ability to do Work

Energy has Two Types: Kinetic (Energy of Motion) Kinetic (Energy of Motion)

and and Potential (Stored Energy)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 Will 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/s2 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 joulesB 64,600 joulesC 93,100 joulesD 121,600 joules

m = 95 kg g = 9.8 m/s2 h = 100 m

95 kg x 9.8 m/s2 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 bodyTemperature 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: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 108 meters through empty space

Heat moves by conduction in solids since the particles are close together

and vibrate. . .

43 Heat convection occurs in gases and liquids. Heat convection does not occur in solids because solids are unable to —

A absorb heat by vibratingB transfer heat by fluid motionC emit radiation by reflecting lightD 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 reflectionG conductionH radiationJ convection

Fluid heat movement is convection. Fluid motion occurs in liquids and gases.

F improve emission of infrared radiationG reduce the heat loss by convection currentsH improve absorption of infrared radiationJ 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 GPainting 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