Chapter Introduction 1.An object sitting on a high shelf has no energy. 2.There are many forms of...
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1. An object sitting on a high shelf has no energy. 2. There are many forms of energy. Do you agree or disagree?
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Transcript of Chapter Introduction 1.An object sitting on a high shelf has no energy. 2.There are many forms of...
1. An object sitting on a high shelf has no energy.
2. There are many forms of energy.
Do you agree or disagree?
• How do potential energy and kinetic energy differ?
• How are mechanical energy and thermal energy similar?
• What two forms of energy are carried by waves?
Forms of Energy
• Energy influences everything in your life, including the climate, the economy, and your body.
• Scientists define energy as the ability to cause change.
Energy
• Potential energy is stored energy due to the interaction between objects or particles.
• Objects have potential energy if they have the potential to cause change.
• Some examples of potential energy are: objects that could fall due to gravity. And particles that can move because of electric or magnetic forces.
Potential Energy
Objects have gravitational potential energy if they have mass and height above Earth’s surface.
• Chemical energy is the energy stored in and released from the bonds between atoms.
• Your body breaks chemical bonds in foods and coverts the released energy into other forms of energy that your body can use.
Potential Energy (cont.)
• The energy stored in and released from the nucleus of an atom is called nuclear energy.
• The Sun’s energy is released through the process of nuclear fusion, during which the nuclei of atoms join together and release large amounts of energy.
Potential Energy (cont.)
• Kinetic energy is energy due to motion.
• An object’s kinetic energy is related to the mass and the speed of the object.
– meaning that if two objects are traveling at the same speed, the one with more mass will have more kinetic energy
• The energy in an electric current is electric energy.
Kinetic Energy
Kinetic Energy (cont.)
Talk to your partners:
How do potential energy and kinetic energy differ?
Kinetic Energy (cont.)
How do potential energy and kinetic energy differ?
Answer: Potential energy is stored, and kinetic energy is energy due to motion.
What kind of energy is shown here?
• Is kinetic energy shown here?
• Is potential energy shown here?
• Explain both.
The sum of the potential energy and the kinetic energy in a system is mechanical energy.
Combined Kinetic Energy and Potential Energy
The hockey player on the last slide showed both potential and kinetic energy. Therefore the puck had mechanical energy.
Come up with an example of something that has mechanical energy with your partners.
• An object’s thermal energy is the sum of the kinetic energy and the potential energy of the particles that make up the object.
• Thermal energy of an object increases when the potential energy, the kinetic energy, or both increase.
Combined Kinetic Energy and Potential Energy (cont.)
Combined Kinetic Energy and Potential Energy (cont.)
What is the same and what is different about mechanical energy and thermal energy?
Combined Kinetic Energy and Potential Energy (cont.)
What is the same and what is different about mechanical energy and thermal energy?
Answer: Both are sums of potential and kinetic energy. Thermal is the sum of the particles in an object, and kinetic is the sum of the parts in a system.
• A wave is a disturbance that transfers energy from one place to another without transferring matter.
• Sound energy is carried by sound waves.
• Light is a form of energy carried by electromagnetic waves, which are electric and magnetic waves moving perpendicular to one another.
• The energy carried by electromagnetic waves is radiant energy.
Energy Carried by Waves
Electromagnetic waves often are described by their wavelengths—the distance from one point on a wave to the nearest point just like it.
• Objects can have potential energy (stored energy) and kinetic energy (energy due to movement).
• Mechanical energy is due to large-scale motions and interactions in a system. Thermal energy is due to atomic-scale motions and interactions in particles.
• Two kinds of energy carried by waves are sound energy and radiant energy.
A. chemical energy
B. kinetic energy
C. mechanical energy
D. nuclear energy
1. Which term describes energy stored in and released from the bonds between atoms?
A. wave
B. wavelength
C. potential energy
D. thermal energy
2. Which refers to a disturbance that transfers energy from one place to another without transferring matter?
A. chemical energy
B. nuclear energy
C. potential energy
D. radiant energy
3. What type of energy provides the warmth from the Sun?
1. An object sitting on a high shelf has no energy.
2. There are many forms of energy.
Do you agree or disagree?
• What is the law of conservation of energy?
• How is energy transformed and transferred?
• What are renewable and nonrenewable energy resources?
Energy Transfers and Transformations
• law of conservation of energy
• energy transfer
• energy transformation
Energy Transfers and Transformations
• work
• open system
• closed system
• renewable energy resource
• nonrenewable energy resource
1. In most systems, no energy is transferred to the environment.
2. Some forms of energy are replenished naturally.
Do you agree or disagree?What do you think?
The law of conservation of energy says that energy can be transformed from one form to another, but it cannot be created or destroyed.
In every energy transformation, some energy transfers to the environment.
Law of Conservation of Energy
The radiant energy that shines out of the flashlight cannot be greater than the chemical energy stored in the battery.
• When energy moves from one object to another without changing form, an energy transfer occurs.
• The mechanical energy of a tennis racket changing the movement of the ball is an example of an energy transfer.
• Come up with your own example of an energy transfer with your partners
Law of Conservation of Energy (cont.)
• When one form of energy is converted to another form of energy, an energy transformation occurs. (click me)
• The conversion of chemical energy stored in a tennis player’s muscle changing to mechanical energy when she swings her arm is an example of an energy transformation.
• Come up with your own example of an energy transformation with your partners.
Law of Conservation of Energy (cont.)
Law of Conservation of Energy (cont.)
Identify an energy transfer and an energy transformation that occurs when someone plays a guitar.
Law of Conservation of Energy (cont.)
Identify an energy transfer and an energy transformation that occurs when someone plays a guitar.
Answer: Chemical energy in the cells is transformed to mechanical energy in the fingers, then transferred to the guitar strings.
Electric energy from the amp is converted into sound energy when the chords are struck.
• To a scientist, work is the transfer of energy that occurs when a force makes an object move in the direction of the force.
• Work is only being done while the force is acting on the object.
• Any time there is an energy transformation or energy transfer, some energy is transformed into thermal energy.
Law of Conservation of Energy (cont.)
• If a tennis player is holding a tennis ball before a serve, is she doing work on the ball?
– Recall that to do work a force must be working on an object.
• Come up with an example of work being done in your everyday life, with your partners.
• Anytime there is an energy transformation or energy transfer, some energy is transformed into thermal energy.
• Energy transformations are inefficient because not all the energy that is transformed to another form of energy is usable.
• Lets go back to the flashlight. In a flashlight the transformation of chemical energy from the battery to radiant energy from the light bulb is inefficient. As the electric energy move through the circuit, some electric energy transforms to thermal energy. This makes the transformation inefficient, and this is why some bulbs are warm.
• With your partners: Explain the above transformation and why its inefficient.
• An open system is a system that exchanges matter or energy with the environment.
• A closed system is a system that does not exchange matter or energy with the environment.
• In reality, there are no closed systems because every physical system transfers some energy to or from its environment.
Law of Conservation of Energy (cont.)
• A renewable energy resource is an energy resource that is replaced as fast as, or faster than, it is used.
• Solar energy from the Sun is one type of renewable energy resource that can be converted into electric energy.
Energy Transformations and Electric Energy
• Wind moves the blades of a wind turbine to generate electric energy.
• In hydroelectric plants, falling water is channeled through a turbine which transforms mechanical energy into electric energy.
Energy Transformations and Electric Energy (cont.)
• Geothermal plants transfer thermal energy from the Earth to water, creating steam that turns turbines in electric generators. (click me)
• Biomass includes wood, plants, manure, and garbage, all of which are sources of stored chemical energy that can be transformed to electric energy in energy plants.
Energy Transformations and Electric Energy (cont.)
• Nonrenewable energy resources are energy resources that are available in limited amounts or that are used faster than they can be replaced in nature.
• Fossil fuels include petroleum, natural gas, propane and coal.
• In nuclear energy plants, uranium atoms are split apart in a process called nuclear fission.
Energy Transformations and Electric Energy (cont.)
Most of the energy used in the United States comes from nonrenewable energy resources.
Energy Transformations and Electric Energy (cont.)
What are renewable and nonrenewable energy resources?
Energy Transformations and Electric Energy (cont.)
What are renewable and nonrenewable energy resources?
Renewable: energy resource that is replaced as fast or fast than it is used
Nonrenewable: energy resource that is available in limited amounts or is used faster than can be replaced in nature
• Energy can be transferred and transformed, but it cannot be created or destroyed.
• Systems are classified as open systems or closed systems based on their interactions with their environment.
• Energy resources are classified as renewable or nonrenewable based on their abundance and availability.
A. conservation
B. work
C. closed system
D. open system
1. Which term refers to the transfer of energy that occurs when a force makes an object move in the direction of the force?
A. closed system
B. energy resource
C. geothermal energy
D. open system
2. A car’s engine is an example of which of these?
A. open system
B. solar energy
C. nonrenewable energy resource
D. renewable energy resource
3. Which is an example of biomass?
1. In most systems, no energy is transferred to the environment.
2. Some forms of energy are replenished naturally.
Do you agree or disagree?
