Chapter 15 Energy Energy and Work Energy: The ability to do work.
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Transcript of Chapter 15 Energy Energy and Work Energy: The ability to do work.
Chapter 15
Energy
Energy and Work
Energy: The ability to do work.
Work
The transfer of energy as the result of motion.
(Unit of Work is the Joule)
Work = Force x distanceW = F x d
Joule (J)
Unit of Energy and Work. W = F • d
Joule = Newton • meterJ = (kg • m/s²) • m
Kinetic Energy (KE)
Energy that appears in the form of motion.
Kinetic Energy (KE)
KE = ½ mv2
m
A 70.0-kilogram daemon is walking at a speed of 2.0 m/s. What is his kinetic energy?
Given: m = 70.0kg v = 2 m/s
Find: KE = ?
KE = 140J
Equation: KE = ½ mv2
Solve: KE = ½ (70.0kg)(2 m/s)2
Potential Energy (PE)
Energy that an object has as the result of its position or condition.
Gravitational Potential Energy (GPE)
An object's gravitational potential energy depends on its
mass, its height, and the acceleration due to
gravity.
m
h
PE = mghm = mass
h = height g = acceleration due to gravity(9.8m/s2)
Suppose the diver at the top of a 10.0-meter-high diving platform has a mass of 50.0 kilograms.
Given: m = 50.0 kg h = 10 m
g = 9.8 m/s2
Find: GPE = ?
GPE = 4900J
Equation: GPE = mgh
Solve: GPE = (50.0kg)(9.8 m/s2)(10m)
Elastic Potential Energy
The potential energy of an object that is stretched or compressed.
Forms of Energy
The major forms of energy are mechanical energy, thermal
energy, chemical energy, electrical energy, electromagnetic energy,
and nuclear energy.
Mechanical Energy
Kinetic Energy and
Potential Energy
ME = KE + PE
Thermal Energy
The total potential and kinetic energy of all the microscopic
particles in an object
Chemical Energy
The energy stored in chemical bonds.
Electrical EnergyEnergy associated with
electric charges.
Electromagnetic EnergyForm of energy that travels through
space in the form of waves.
Nuclear Energy
The energy stored in atomic nuclei.
Nuclear Fission
NuclearFusion
NuclearFusion
HomeworkMath Practice
Page 448, Probs:1-3
Section 15.1WorksheetDue: 4/29/10
Law of Conservation of Energy
•Can change from one form to another.• Can never be created or destroyed. •Total energy of the universe remains the same.
Energy:
Mechanical Energy = Potential Energy + Kinetic Energy
E = PE + KE
KE = 0PE = max
KE = 0PE = maxKE = max
PE = 0
Pol
e V
ault
Kinetic Energy
ElasticPotential
Energy
Kinetic Energy
Gravitational Potential Energy
E - Energym - mass c – speed
oflight
Work
PE
KE + PE
KE + PE
Homework 15-2
Section 15-2WorksheetDue: 4/7/09
Nonrenewable EnergyA source of energy that exists in limited quantities and, once used, cannot be replaced except over the
course of millions of years.
Nonrenewable EnergyNonrenewable energy
resources include oil, natural gas, coal, and uranium
Renewable Energy
A source of energy that can be replaced in a relatively
short period of time.
Renewable Energy
Renewable energy resources include hydroelectric, solar, geothermal, wind, biomass, and, possibly in the future,
nuclear fusion.
Hydroelectric
Solar
Geo
ther
mal
Win
d
Biomass
Homework 15-3
Section 15-3Worksheet
D: Due: 4/8/09
Homework 15-3Section 15-3Worksheet
D: Due: 4/8/09F: Due: 4/7/07D Test: 4/9/08
F Test: 4/11/08
Homework 15 -3Section 15-3
Word-wise/MathWorksheetsDue: 5/5/10
D Test: 5/6/10E Test: 5/7/10
Temperature and Heat
Temperature: The measure of the average kinetic energy of the particles
in a sample of matter.
Thermal Energy
The total energy of the particles in a material.
25ºC
25ºC
Heat
The flow of Thermal Energy.
Heat is the flow of Thermal Energy from an area of
High Temperature to one of
Low Temperature.
Thermal Pollution
Waste you can’t see!!!
Thermal Pollution: Occurs when waste heat significantly changes the
temperature of the environment.
Adding warm water to lakes, rivers and oceans can change the environment.
How?
Homework 5-2
Section Wrap-upPage: 137
Section Wrap-upPage: 140
Due: 11/7/05
Projects Due
Tomorrow11/04/05
Measuring Thermal Energy
Temperature
Type of Material
Mass of Material
MaterialWater Metal
Specific Heat
Specific Heat [C, J / (kg • K)]The amount of energy it takes to it
takes to raise the temperature of 1 kg of material 1 Kelvin. ( K = C )
It takes 4184 joules of energy to raise the temperature of 1 kg of water, 1C.
Material Specific Heat
Water 4184 J / (kg • K)Alcohol 2450 J / (kg • K)
Aluminum 920 J / (kg • K)Graphite(Carbon) 710 J / (kg • K)
Sand 664 J / (kg • K)Iron 450 J / (kg • K)
Copper 380 J / (kg • K)Silver 235 J / (kg • K)
Calculating Thermal Changes
Specific Heat - C
Change in Thermal Energy - QMass - m
Change in Temperature - T
Q = m • T • C
T = Tfinal - Tinitial
Example: Mr. Clune wants to bring 1 kg of water to boiling for his
afternoon tea. The temperature of the water out of the tap is 10C. How much Thermal Energy does he have
to add to the water?
Given: m = 1 kg Find: Q = ?Tinitial = 10C Tfinal = 100CC = 4184 (J / (kg • C ) )
Equation: Q = m • T • C Q = m • (Tfinal - Tinitial) • C
Solve: Q = (1 kg) • (100C -10C) • 4184(J/(kg • C)Q = (1 kg) • (90C) • 4184 (J/(kg • C)
Q = 377,000 J or 377 kJ
Example: Do the same problem as the one above but use sand instead.Given: m = 1 kg Find: Q = ?
Tinitial = 10C Tfinal = 100CC = 664 (J / (kg • C ) )
Equation: Q = m • T • C Q = m • (Tfinal - Tinitial) • C
Solve: Q = (1 kg) · (100C -10C) · 664(J/(kg.C)
Q = 60,000 J or 60 kJ
Homework 5-4Practice Problem: 1-2
Page:143Section Wrap-up
Page: 144Due: 11/09/05
Test on 11/15/05
Homework 5-5
Vocabulary: 1-10Page:147
Review Questions:1-25Page: 148-149Due: 11/22/04Test: 11/23/04