Chapter 9: Energy Material on Final Exam

Section 9-1—What is Energy Objectives Explain the relationship between energy and work. Compare kinetic energy and potential energy. Describe the different forms of energy.

Section 9-1—What is Energy Energy is known by the changes it causes Energy is the ability to do work. Work is the transfer of energy. Work and Energy are closely related: Energy is transferred by a force moving an object through a distance.

Section 9-1—What is Energy Work and energy are both expressed in SI units known as a Joule (J). How big (or small) is a Joule? There are 4.184 J in a calorie Your food Calories are actually kcal—1000 calories! A 2000kcal diet would be 8368000 Joules!

Section 9-1—What is Energy Types of Energy We break energy down into several categories Mechanical energy Kinetic Potential Thermal energy Chemical energy Electrical energy Electromagnetic energy Nuclear energy

Section 9.1—What is energy? Energy can constantly switch forms

Section 9-1—What is Energy Mechanical energy Mechanical Energy is the energy associated with the motion and position of objects. Both kinetic energy and potential energy are examples of mechanical energy. Examples: speeding train bouncing balls, sprinting athletes, baseball falling through the air. FORMULA ME= (KE+PE)

Section 9-1—What is Energy

Section 9-1—What is Energy Math practice Balls being juggled by a juggler has a potential energy of 20 J and kinetic energy of 600 J. What is the ball’s total mechanical energy? You try! Let’s say a pin being juggled by a juggler has a potential energy of 30 J and the kinetic energy of 500 J. What is the pin’s mechanical energy?

Section 9-1—What is Energy A roller coaster has the potential energy of 10,000 J and the kinetic energy of 50,000 J. What is the coaster’s mechanical energy?

Section 9-1—What is Energy A. Kinetic energy The energy of motion. All moving objects have kinetic energy. Kinetic Energy of any moving object depends upon its mass and speed. FORMULA - SI Unit = Joule KE = mv2 2

Section 9-1—What is Energy No formula triangle? Because of the squared part, we cannot use a formula triangle. You can rewrite the formulas.. But it’s easier to do the algebra m = 2(KE) V = 𝟐(𝑲𝑬) 𝒎 v2

Section 9-1—What is Energy Math practice A 70 kg man is walking at a speed of 2 m/s. What is his kinetic energy? You try! A 1400 kg cart moves at 25 m/s. What is the cart’s kinetic energy?

Section 9-1—What is Energy A 50 kg cheetah has a KE of 18,000J. How fast is the cheetah running?

ANSWER MUST BE 3 LINES OF TEXT FOR FULL CREDIT! PROCESS BOX 1 What would you need to do to maximize kinetic energy? What would you need to do to minimize kinetic energy? ANSWER MUST BE 3 LINES OF TEXT FOR FULL CREDIT!

Section 9-1—What is Energy B. Potential Energy Potential Energy is energy stored as a result of position or shape. Examples: rock on a cliff, rubber band, wind up toy. Gravitational Potential Energy depends on an objects weight (mass) and height. This type of energy increases when an object is raised to a higher level. Gravitational potential energy is equal to the amount of work done on an object to lift it a certain height.

Section 9-1—What is Energy

Section 9-1—What is Energy FORMULA – PE = m g h or PE = wh REMEMBER – weight = force To get weight, do mass (kg) x gravity

Section 9-1—What is Energy Math practice What is the gravitational potential energy of a cat that weighs 40 N standing on a table that is 0.8 m above the ground? You try! What is the gravitational potential energy of a diver who weighs 500 N standing on a platform that is 10 m off the ground?

Section 9-1—What is Energy What is the gravitational potential energy of a diver who has a mass of 61 kg standing on a platform that is 8 m off the ground?

ANSWER MUST BE 3 LINES OF TEXT FOR FULL CREDIT! PROCESS BOX 2 Where would you put an object to maximize its GPE? Where would GPE be zero? ANSWER MUST BE 3 LINES OF TEXT FOR FULL CREDIT!

Section 9-1—What is Energy Thermal Energy Thermal (heat) Energy - is all of the kinetic energy due to random motion of the particles that make up an object. All matter has thermal energy because all particles are in constant random motion.

Section 9-1—What is Energy Thermal energy and speed As temperature increases, the atoms move faster. The faster the atoms move, the higher thermal energy.

Section 9-1—What is Energy Chemical Energy Chemical Energy is the energy of a chemical compound that changes as its atoms are rearranged. It is the energy stored in the chemical bonds in compounds. When the bonds break energy is released. Examples include: Gasoline/coal Food Wood

Section 9-1—What is Energy Electrical Energy Electrical Energy is the energy associated with electric charges. Electric charges can exert forces that do work. Examples include: Batteries lightning

Section 9-1—What is Energy Electromagnetic Energy Electromagnetic Energy is a form of energy that travels through space in the form of waves. Sun (visible light) Stars Galaxies Radio waves X-rays

Section 9-1—What is Energy

Section 9-1—What is Energy Nuclear Energy Nuclear Energy is the energy stored in the nuclei of atoms. Nuclear fission is a process of releasing energy through splitting nuclei apart. Nuclear Fusion releases energy when a less massive nuclei combine to form a more massive nucleus.

ANSWER MUST BE 2 LINES OF TEXT FOR FULL CREDIT! PROCESS BOX 3 Explain three different energy forms that would be found in the process of burning wood to boil water to make steam. ANSWER MUST BE 2 LINES OF TEXT FOR FULL CREDIT!

Section 9-1—What is Energy Objectives Please answer the following on your objectives sheet Explain the relationship between energy and work. Compare kinetic energy and potential energy. Describe the different forms of energy.

Section 9-2 & 9-3—Energy Conversions Objectives Describe an energy conversion. Give examples of energy conversions for the different forms of energy. Explain how energy conversions make energy useful. Explain the law of conservation of energy. Give examples of how thermal energy is always a result of energy conversion.

Section 9-2 & 9-3—Energy Conversions Law of Conservation of Energy Energy can not be created or destroyed. Energy can be converted from one form to another. Any form of energy can change into any other form of energy.

Section 9-2 & 9-3—Energy Conversions In energy conversions, some energy is always lost as heat (Thermal energy). After energy conversions, you always end up with the same total amount of energy as the original amount of potential energy.

Section 9-2—Energy Conversions

Section 9-2—Energy Conversions

Section 9-2 & 9-3—Energy Conversions In lighting a match, your muscles use chemical energy moving your hand to strike the match, friction converts some of the matches kinetic energy into thermal energy. The thermal energy triggers a chemical reaction on the match tip, releasing some of the match’s chemical energy. The stored chemical energy is then converted into thermal energy and electromagnetic energy in the flame.

Section 9-2 & 9-3—Energy Conversions Alarm Clock Battery Light Bulb Blender Hair Dryer Light & sound energy (electromagnetic) Electrical energy Chemical energy Electrical energy Light (electromagnetic) & thermal energy Electrical energy Kinetic & sound (electromagnetic) energy Electrical energy Thermal & sound (electromagnetic) energy Electrical energy

PROCESS BOX 4 Where in a roller coaster would you have all KE? Where would you have all PE?

Section 9-2 & 9-3—Energy Conversions Objectives Please answer the following on your objectives sheet Describe an energy conversion. Give examples of energy conversions for the different forms of energy. Explain how energy conversions make energy useful. Explain the law of conservation of energy. Give examples of how thermal energy is always a result of energy conversion.

Section 9.4—Energy Resources Objectives Explain the difference between nonrenewable resources and renewable resources. Name several energy resources.

Section 9.4—Energy Resources Nonrenewable Resources Nonrenewable resources cannot be replaced or are replaced much more slowly than they are used. Fossil fuels are nonrenewable energy resources that formed from the remains of organisms that lived long ago. Examples include: Oil, natural gas, and coal are the most common fossil fuels.

Section 9.4—Energy Resources Burning coal is a common way to generate electrical energy. Petroleum is used to make gasoline, wax, and plastics. Natural gas is often used in home heating. The United States’ primary source of electrical energy is generated by burning fossil fuels.

Section 9.4—Energy Resources

Section 9.4—Energy Resources How do we make electricity from these resources? Electric generators convert the chemical energy in fossil fuels into electrical energy by the process shown below. An electric generator converts energy of one type into another type of energy.

Section 9.4—Energy Resources Renewable Resources Renewable resources are naturally replaced more quickly than they are used. Solar Energy Sunlight can be changed into electrical energy through solar cells. Energy from Water The potential energy of water in a reservoir can be changed into kinetic energy as the water flows through a dam. Wind Energy The kinetic energy of wind can turn the blades of a windmill or a wind turbine.

Section 9.4—Energy Resources

Section 9.4—Energy Resources Objectives Please answer the following on your objectives sheet Explain the difference between nonrenewable resources and renewable resources. Name several energy resources.