chapter menu chapter introduction lesson 1lesson 1types of energy lesson 2lesson 2energy...
TRANSCRIPT
Chapter Introduction
Lesson 1 Types of Energy
Lesson 2 Energy Transformations and Work
Lesson 3 Machines
Chapter Wrap-Up
What do you think?
Before you begin, decide if you agree or disagree with each of these statements. As you view this presentation, see if you change your mind about any of the statements.
1. Energy is the ability to produce motion.
2. Waves transfer energy from place to place.
3. Energy cannot be created or destroyed, but it can be transformed.
Do you agree or disagree?
4. Work describes how much energy it takes for a force to push or to pull an object.
5. All machines are 100 percent efficient.
6. Simple machines do work using one motion.
Do you agree or disagree?
• What is energy?
• What are the different forms of energy?
• How is energy used?
Types of Energy
• energy
• kinetic energy
• electric energy
• potential energy
• chemical energy
• nuclear energy
Types of Energy
• mechanical energy
• thermal energy
• sound energy
• seismic energy
• radiant energy
• Energy is the ability to cause a change.
• Wind, coal, nuclear fuel, Earth’s interior, and the Sun also are sources of energy that can be transformed into other forms of energy, such as electrical energy.
What is energy?
• Kinetic energy is the energy an object has because it is in motion.
• Anything that is in motion has kinetic energy, including large objects that you can see as well as small particles, such as molecules, ions, atoms, and electrons.
Kinetic Energy
• Electrons move around the nucleus of an atom, and they can move from one atom to another.
• When electrons move, they have kinetic energy and create an electric current.
• The energy that an electric current carries is a form of kinetic energy called electric energy.
Kinetic Energy (cont.)
When the blades of wind turbines rotate, they turn a generator that changes the kinetic energy of the moving blades into electric energy.
The McGraw-Hill Companies, Inc./John Flournoy, photographer
• Kinetic energy depends on mass.
• If the turbine blades were smaller and had less mass, they would have less kinetic energy.
Kinetic Energy (cont.)
• Kinetic energy also depends on speed.
• When the wind blows harder, the blades move faster and have more kinetic energy.
Kinetic Energy (cont.)
Kinetic Energy (cont.)
electric
from Greek electrum, means “amber”; because electricity was first generated by rubbing pieces of amber together
• Potential energy is stored energy that depends on the interaction of objects, particles, or atoms.
• Gravitational potential energy is a type of potential energy stored in an object due to its height above Earth’s surface.
Potential Energy
• Gravitational potential energy depends on the mass of an object and its distance from Earth’s surface.
• The more mass an object has and the greater its distance from Earth, the greater its gravitational potential energy.
Potential Energy (cont.)
Hydroelectric energy plants convert the gravitational potential energy of water into electric energy.
• Most electric energy in the United States comes from fossil fuels such as petroleum, natural gas, and coal.
• The atoms that make up these fossil fuels are joined by chemical bonds.
• Chemical energy is energy that is stored in and released from the bonds between atoms.
Potential Energy (cont.)
When fossil fuels burn, the chemical bonds between the atoms that make up the fossil fuel break apart. When this happens, chemical energy transforms to thermal energy.
This energy is used to heat water and form steam. The steam is used to turn a turbine, which is connected to a generator that generates electric energy.
• A drawback of fossil fuels is that they introduce harmful waste products, such as sulfur dioxide and carbon dioxide, into the environment.
• Scientists are searching for replacement fuels that do not harm the environment.
Potential Energy (cont.)
• Chemical energy also is stored in the foods you eat.
• Your body converts the energy stored in chemical bonds in food into the kinetic energy of your moving muscles and into the electric energy that sends signals through your nerves to your brain.
Potential Energy (cont.)
• The majority of energy on Earth comes from the Sun.
• Nuclear fusion, a process found in the Sun, joins the nuclei of atoms and releases large amounts of energy.
Potential Energy (cont.)
Nuclear energy plants break apart the nuclei of certain atoms using a process called nuclear fission.
Nuclear fission produces a large amount of energy from just a small amount of fuel.
• Both nuclear fusion and nuclear fission release nuclear energy—energy stored in and released from the nucleus of an atom.
• Nuclear fission produces radioactive waste that is hazardous and difficult to dispose of safely.
Potential Energy (cont.)
Objects such as wind turbine blades and particles, such as molecules, ions, atoms, and electrons, often have kinetic and potential energies.
Kinetic and Potential Energies Combined
• The sum of potential energy and kinetic energy in a system of objects is mechanical energy.
• Mechanical energy is the energy an object has because of a combination of the following:
• the movement of its parts (kinetic energy)
• the position of its parts (potential energy)
Kinetic and Potential Energies Combined (cont.)
• Thermal energy is the sum of the kinetic energy and potential energy of the particles that make up an object.
• Individual particles vibrate back and forth in place, giving them kinetic energy.
• The particles also have potential energy because of the distance between particles and the charge of the particles.
Kinetic and Potential Energies Combined (cont.)
• The particles in Earth’s interior contain great amounts of thermal energy.
• This energy is called geothermal energy.
Kinetic and Potential Energies Combined (cont.)
Geothermal energy plants turn water into steam, which turns turbines in electric generators that covert the geothermal energy to electric energy.
• Waves are disturbances that carry energy from one place to another.
• Sound energy is energy carried by sound waves.
• Some animals, such as bats, emit sound waves to find prey
Energy from Waves
CORBIS
• The kinetic energy of tectonic plate movement is carried through the ground by seismic waves.
• Seismic energy is the energy transferred by waves moving through the ground.
Energy from Waves (cont.)
Seismic energy can destroy buildings and roads.
Dr. Roger Hutchinson/NOAA
• Electromagnetic waves are electric and magnetic waves that move perpendicular to each other.
• Some electromagnetic waves can travel through solids, liquids, gases, and vacuums.
Energy from Waves (cont.)
Energy from Waves (cont.)
vacuum
Science Use a space that contains no matter
Common Use to clean with a vacuum cleaner or sweeper
• The energy carried by electromagnetic waves is radiant energy.
• The Sun’s energy is transmitted to Earth by electromagnetic waves.
Energy from Waves (cont.)
Radio waves, light waves, and microwaves are all electromagnetic waves.
• Wind turbines have different kinds of energy including kinetic, mechanical, potential, and thermal.
• Nuclear fuel pellets contain potential energy that is stored in the nuclei of atoms.
The McGraw-Hill Companies, Inc./John Flournoy, photographer
Which energy type is stored in and released from the bonds between atoms?
A. chemical
B. electrical
C. kinetic
D. potential
A. geothermal energy
B. nuclear fission
C. nuclear fusion
D. seismic energy
Which term refers to thermal energy that originates from particles in the Earth’s interior?
A. mechanical
B. radiant
C. seismic
D. thermal
Which energy type is carried by electromagnetic waves?
1. Energy is the ability to produce motion.
2. Waves transfer energy from place to place.
Do you agree or disagree?
• What is the law of conservation of energy?
• In what ways can energy be transformed?
• How are energy and work related?
Energy Transformations and Work
• energy transformation
• law of conservation of energy
• work
Energy Transformations and Work
• Energy transformation is the conversion of one form of energy to another.
• When energy is transferred, the form of energy does not have to change.
Energy Transformations
• The law of conservation of energy says that energy can be transformed from one form to another, but it cannot be created or destroyed.
• Even though energy can change forms, the total amount of energy in the universe does not change. It just changes form.
Energy Conservation
What is the law of conservation of energy?
Energy Conservation (cont.)
When you ride a roller coaster, your gravitational potential energy is transformed to kinetic energy and back to gravitational potential energy.
• When a plant carries on photosynthesis, it transforms radiant energy from the Sun into chemical energy.
• The chemical energy is stored in the bonds of the plant’s molecules.
Energy Conservation (cont.)
• When electric energy plants burn fossil fuels, they transform the chemical energy from the molecules that were made by plants that lived millions of years ago.
• That chemical energy is transformed to the electric energy that you use in your home and school.
Energy Conservation (cont.)
Identify three energy transformations that occur to make electric energy.
Energy Conservation (cont.)
• Work is the transfer of energy that occurs when a force makes an object move in the direction of the force while the force acts on the object.
• Forces are pushes or pulls.
Energy and Work
The student does work on the drums when he lifts them. Once the drums are in place, no work is being done.
Energy and Work (cont.)
If you do work on an object, how will its energy change?
• To do work on an object, an object must move in the direction of the force.
• Work is done only while the force is moving the object.
Energy and Work (cont.)
• Work also depends on the distance an object moves during the time the force is applied.
• The equation for work is shown below.
Energy and Work (cont.)
• Force is the force applied to the object. Distance is the distance the object moves in the direction of the force while the force is acting on it.
• The force in the equation is in newtons, and distance is in meters.
• The product of newtons and meters is newton-meter.
• A newton-meter is a joule.
Energy and Work (cont.)
• Friction is a force between two surfaces in contact with each other.
• The direction of friction is in the opposite direction of the motion.
• In every energy transformation and every energy transfer, some energy is transformed into thermal energy.
Energy and Heat
• This thermal energy is transferred to the surroundings.
• Thermal energy moving from a region of higher temperature to a region of lower temperature is called heat.
• Scientists sometimes call this heat waste energy because it is not easily used to do useful work.
Energy and Heat (cont.)
• Energy is always conserved.
• Energy can be transformed into different kinds of energy.
• Work and energy are related.
Which energy type is radiant energy from the Sun transformed into during photosynthesis?
A. chemical
B. kinetic
C. mechanical
D. thermal
A. energy transfer
B. energy transformation
C. law of conservation of energy
D. work
Which term refers to the conversion of one form of energy to another?
A. thermal
B. radiant
C. kinetic
D. chemical
In every energy transformation, some energy is transformed into what type of energy??
3. Energy cannot be created or destroyed, but it can be transformed.
4. Work describes how much energy it takes for a force to push or to pull an object.
Do you agree or disagree?
• What are simple machines?
• In what ways can machines make work easier?
Machines
• simple machine
• inclined plane
• screw
• wedge
• lever
Machines
• wheel and axle
• pulley
• complex machine
• efficiency
• Many machines transfer mechanical energy from one object to another.
• Simple machines are machines that do work using one movement.
Machines Transfer Mechanical Energy
• Simple machines do not change the amount of work required to do a task; they only change the way work is done.
• A simple machine can be an inclined plane, a screw, a wedge, a lever, a pulley, or a wheel and axle.
Machines Transfer Mechanical Energy (cont.)
• An inclined plane is a flat, sloped surface.
• A screw is an inclined plane wrapped around a cylinder.
The McGraw-Hill Companies, Inc./Jacques Cornell photographer
• A wedge is an inclined plane that moves.
• A lever is a simple machine that pivots around a fixed point.
• A wheel and axle is a simple machine that is a shaft attached to a wheel of a larger diameter so that both rotate together.
• A pulley is a grooved wheel with a rope or cable wrapped around it.
Dynamic Graphics/Jupiterimages
What are examples of simple machines?
Machines Transfer Mechanical Energy (cont.)
• Two or more simple machines working together are a complex machine.
• Complex machines use more than one motion to accomplish tasks.
Machines Transfer Mechanical Energy (cont.)
• The work you do on a machine is called the input work.
• The work the machine does on an object is the output work.
• Machines make work easier by changing the distance the object moves or the force required to do work on an object.
Machines and Work
• When the input distance of a machine is larger than the output distance, the output force is larger than the input force.
• Machines also can change the direction of a force.
Machines and Work (cont.)
The window washer’s pulley system makes the work of lifting easier.
• Input and output work are measured in joules.
• Efficiency is expressed as a percentage by multiplying the ratio by 100%.
Efficiency (cont.)
• The efficiency of a machine is never 100%—some work is always transformed into wasted thermal energy because of friction.
• Lubricating the moving parts of a machine reduces the friction between the moving parts so that less input work is transformed to waste energy.
Efficiency (cont.)
Efficiency (cont.)
efficiency
from Latin efficere, means “work out, accomplish”
Newton’s third law says that if one object applies a force on a second object, the second object applies an equal and opposite force on the first object.
Newton’s Laws and Simple Machines
According to Newton’s first law, the motion of an object changes when the forces that act on the object are unbalanced.
Newton’s Laws and Simple Machines (cont.)
According to Newton’s second law of motion, the change in motion of an object is in the same direction as the total, or net.
Newton’s Laws and Simple Machines (cont.)
• A bottle opener is a simple machine.
• There are six types of simple machines, and a ramp is one example.
• A bicycle is an example of a complex machine that is made up of different simple machines.
Which type of machine does work using one movement?
A. complex
B. efficient
C. mechanical
D. simple
A. complex machine
B. inclined plane
C. pulley
D. wedge
Which term describes a grooved wheel with a rope or cable wrapped around it?
A. efficiency
B. force
C. friction
D. work
What does lubricating the moving parts of a machine reduce?
5. All machines are 100 percent efficient.
6. Simple machines do work using one motion.
Do you agree or disagree?
Key Concept Summary
Interactive Concept Map
Chapter Review
Standardized Test Practice
Energy causes change by affecting the movement and position of objects. Energy can be transformed from one form to another and transferred from object to object.
• Energy is the ability to cause change.
• Kinetic energy is the energy of objects in motion, including electric energy. The forms of potential energy include gravitational potential energy, chemical energy, and nuclear energy. Thermal energy and mechanical energy are forms of energy involving both kinetic and potential energies. Sound energy, seismic energy, and radiant energy are all transferred by waves.
• Energy is used to move cars, heat homes, produce light, move muscles, catch prey, and cook food among many other examples.
Lesson 1: Types of Energy
Lesson 2: Energy Transformations and Work
• The law of conservation of energy states that energy can be transformed from one form to another, but it can never be created or destroyed.
• Energy can be transformed from one form to another in a variety of ways.
• Doing work on an object transfers energy to the object.
• Simple machines do work using one movement.
• Machines make work easier by changing the size of the force required, the distance over which the object moves, or the direction of the input and output forces.
Lesson 3: Machines
A. chemical
B. kinetic
C. nuclear
D. potential
Which describes stored energy that depends on the interaction of objects, particles, or atoms?
A. fossil fuels
B. the Sun
C. water
D. wind
Where does the majority of energy on Earth come from?
A. energy transformation
B. friction
C. law of conservation of energy
D. work
Which describes how much energy it takes for a force to push or to pull an object?
A. complex machine
B. inclined plane
C. pulley
D. wheel and axle
Which term refers to two or more simple machines working together?
A. lever
B. pulley
C. screw
D. wedge
Which is an inclined plane that wraps around a cylinder?
A. gravitational
B. kinetic
C. mechanical
D. potential
Which refers to the energy an object has because it is in motion?
A. chemical
B. mechanical
C. nuclear
D. sound
Which describes energy stored in and released from the nucleus of an atom?
A. They make it easier to do work.
B. They change the direction of a force.
C. They increase the amount of work done on an object.
D. They reduce the force needed to do the work.
Which is NOT true about what machines are used to do?
A. work
B. simple machine
C. efficiency
D. complex machine
Which term describes the ratio of output work to input work?
A. lever
B. pulley
C. wedge
D. wheel and axle
Which is an inclined plane that moves?