Energy and Heat Table of Contents What Is Energy? Forms of Energy Energy Transformations and Conservation Temperature, Thermal Energy, and Heat The Transfer of Heat

8.1 Vocabulary Energy Kinetic energy Potential energy Gravitational potential energy Elastic potential energy

How are energy, work, and power related? Work is done when a force moves an object. When you do work on an object, some of your energy is transferred to that object. Energy is measured in joules, the same unit as work.

Power is the rate at which work is done. Since the transfer of energy is work, the power is the rate at which energy is transferred, or the amount of energy transferred in a unit of time. Power = Energy Transferred / Time Using a machine to do work allows the same amount of energy in a shorter amount of time What is energy?

What are two types of energy? The two basic types of energy are kinetic energy and potential energy. Whether energy is kinetic or potential depends on the motion, position, and shape of the object.

What Is Energy? A moving object can do work when it strikes another object and moves it. Kinetic Energy The kinetic energy of an object depends on its speed and mass.

Factors Affecting Kinetic Energy The faster an object moves, the more kinetic energy it has. Kinetic energy also increases as mass increases.

Calculating Kinetic Energy Formula for KE: KE = (1/2)(Mass)(Speed)2 So, a boy pulling a 10-kg wagon at a speed of 2 m/s: KE = (1/2)(10kg)(2m/s)2 = Note that 1 kg·m2/s2 = 1 joules (J)

Do changes in the mass and speed have the same effect Do changes in the mass and speed have the same effect? KE = (1/2)(10kg)(2m/s)2= 20 J Double the mass: KE = (1/2)(20kg)(2m/s)2 = Double the speed: KE = (1/2)(10kg)(4m/s)2 Why does this work this way?

An object does not have to be moving to have energy. Potential Energy An object does not have to be moving to have energy. Some objects have energy as a result of their shapes or positions. You can transfer energy and the object can store it for future movement. It has the potential to do work.

What Is Energy? Gravitational Potential Energy The rock climbers have gravitational potential energy, which is potential energy related to an object's height. The gravitational potential energy of an object is equal to the work done to lift it to that height.

Gravitational Potential Energy Since work is equal to force multiplied by distance, you can calculate an object’s gravitational potential energy: gravitational potential energy = weight x height So if a book has a weight of 10 N and is lifted 2 m off the ground, how much gravitational potential energy does it have?

Elastic Potential Energy Objects that can be compressed or stretches have a different type of energy. When a rubber band is stretched or a spring is squeezed, it has elastic potential energy. The more the object is stretched or compressed, the more elastic potential energy it has.

What Is Energy? Elastic Potential Energy The energy stored in a stretched object, such as the trampoline, is elastic potential energy. Using 1 as the greatest, how would you rank the amount of elastic potential energy of the trampoline from greatest to least?

What Is Energy? What is the SI unit for each quantity?

8.2 Forms of Energy Calculating Mechanical Energy Form of energy associated with the motion, position, or shape of an object is called mechanical energy. ME is a combination of its potential energy and its kinetic energy: the higher an object moves, the greater the PE, the faster an object moves, the greater the KE. Find the ME by adding together the object’s kinetic energy and potential energy.

An object with mechanical energy can do work on another object. The more mechanical energy an object has, the more work it can do. ME

Forms of Energy Nuclear Energy Use the Venn diagram to compare and contrast nuclear fission and nuclear fusion.

Forms of Energy Forms of Energy Many objects in this restaurant have more than one form of energy. Find three objects.

Energy Transformations and Conservation Multiple Transformations A series of energy transformations must occur for you to ride your bike. What are the forms of energy involved in each transformation?

Energy Transformations and Conservation Pendulum A continuous transformation between potential and kinetic energy occurs in a pendulum. What are the types of energy the pendulum has at positions A, B, and C?

Energy Transformations and Conservation Conserving Energy While You Ride Transformations between potential and kinetic energy occur during a roller coaster ride. How much potential and kinetic energy does the coaster have at each point?

Temperature, Thermal Energy, and Heat Temperature Scales The chart shows a weather report, but it does not identify the temperature scale. Which row of temperatures do you think represents Celsius?

Temperature, Thermal Energy, and Heat The total amount of thermal energy in an object depends on its temperature and how many particles it contains. In the top two diagrams, which chicken pot pie contains more thermal energy? How should the bottom diagram be completed to show three pies with more thermal energy than the first?

The Transfer of Heat Where Does Heat Transfer on This Beach? Heat transfer goes on all around you all the time, even on the beach.

The Transfer of Heat Type of Heat Transfer Describe the different types of heat transfer in the illustration.

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