Energy and Energy Resources Pages 240 to 247 Chapter 9 Energy and Energy Resources Pages 240 to 247

Terms to Learn Energy: the ability to do work. Kinetic Energy: the energy of motion(KE) depends on speed and mass Potential Energy: the energy of position or shape.(PE)

ENERGY Energy is the ability to do work; work is the transfer of energy. Both energy and work are expressed in Joules (J).

ENERGY The tennis player is doing work on her racket because she has energy When she does work on the racket, the racket gains the ability to do work on the ball.

Energy is transferred from the tennis player to the racket. When the racket does work on the ball, the ball gains the ability to do work on something else. Energy is transferred from the racket to the ball.

Kinetic Energy (K.E.) TYPES OF ENERGY Depends on: Speed and Mass Speed has more of an effect on Kinetic Energy than mass because speed is squared in the equation.

Kinetic Energy Kinetic energy=mv2 2 m=mass (kg) v=velocity (m/s) KE=Joules As the roller coaster descends its velocity increases causing the roller coaster to gain kinetic energy.

Forms of Energy Thermal energy Chemical energy Electrical energy Sound energy Light energy Nuclear energy

FORMS OF ENERGY Thermal energy – the total energy of the particles that make up an object. The higher the temperature, the faster particles move and the more K.E. they have Thermal energy also depends on the number of particles there are in a substance. See Figure 5 on p. 244

FORMS OF ENERGY Chemical energy – the energy of a compound that changes as its atoms are rearranged to form new compounds. Chemical energy is a form of potential energy.

Electrical Energy Is the energy of moving electrons Both kinetic and potential energy

Sound Energy Is caused by an object’s vibrations It is a form of potential and kinetic energy

Light Energy Is produced by the vibrations of electrically charged particles Kinetic energy

Nuclear Energy The energy associated with changes in the nucleus of an atom Nuclear power plants use uranium, a radioactive element, to create electricity. Potential Energy

POTENTIAL ENERGY Also known as P.E. or G.P.E. Energy of position or shape Gravitational potential energy depends on: Weight and Height (distance above Earth’s surface)

POTENTIAL ENERGY The stored potential energy of the bow and string allows them to do work on the arrow when the string is released

PE = mass ● g ● height GPE = weight ● height Weight = mass ● g POTENTIAL ENERGY PE = mass ● g ● height or GPE = weight ● height Weight = mass ● g

GPE is measured in Joules (J) mass is measured in kg Potential Energy GPE is measured in Joules (J) mass is measured in kg height is measured in meters (m) g is acceleration due to gravity and is a constant number- 9.8 m/s2

Energy Partners

Terms to Learn Mechanical Energy: is the total energy of motion and position of an object. It can be all potential energy, all kinetic energy, or some of both. Mechanical energy = potential energy + kinetic energy ME=PE+KE

Mechanical Energy When potential energy increases (or decreases), kinetic energy has to decrease (or increase) in order for mechanical energy to remain constant.

Chapter 9 Energy Is Conserved Within a Closed System Conservation of Energy Energy Is Conserved Within a Closed System A closed system is a group of objects that transfer energy only to each other. The Law of Conservation of Energy states that energy cannot be created or destroyed. Energy can be converted from one form to another. But all of the different forms of energy in a system always add up to the same total amount of energy.

No Conversion Without Thermal Energy During energy conversions some of the original energy is always converted into thermal energy This is due to friction This energy is not always useful