Chapter 13: Energy

Section 1: What is Energy?

What is Energy?

The ability to do work or cause change.

What are the different forms of Energy?

• Energy has a number of different forms, all of which measure the ability of an object to do work on or change another object.

• In other words, there are different ways that an object can possess energy.

What are the different forms of Energy?

• Kinetic Energy• Potential Energy• Thermal, or heat energy• Chemical Energy• Electrical Energy• Electrochemical Energy• Electromagnetic Energy (light)• Sound Energy• Nuclear Energy

Mechanical Energy

Define Potential Energy

Potential energy is energy due to position or stored energy. Potential energy is also called gravitational potential energy.

How do we calculate potential energy?

• PE = weight x height

• A 4 newton rock is sitting on a 3m ledge. What is its potential energy?

• Answer: 12 joules

Give an example of potential energy

By stretching a rubber band, you give it potential energy. A vase on a shelf has stored potential energy. A football being held by a quarterback has potential energy until it is thrown and it turns into kinetic energy.

Define Kinetic Energy

Kinetic energy is the energy of motion. Kinetic energy is measured by how much is work done to put an object in motion or to rest.

How do we calculate kinetic energy?

• KE = mass x velocity2

2

• Example: A 3 kg ball is rolling 2m/s. How much kinetic energy does it have?

• Answer: 3 joules

Give an example of kinetic energy

A basketball player has kinetic energy. The movements that she does show the energy that is being displayed while she is moving. When you are running, walking, or jumping, your body is exhibiting kinetic energy.

Give an example of something that has both

potential and kinetic energy.

A waterfall has both kinetic and potential energy. The water at the top of the waterfall has stored potential energy. Once the water leaves the top of the waterfall, the potential energy is changed into kinetic energy.

Click this link for more information about potential &

kinetic energy. Remember to hit the “back” button on your

browser to return to this slide show.

http://www.usoe.k12.ut.us/curr/science/sciber00/8th/forces/sciber/potkin.htm

Describe Conservation of Energy

Energy cannot be created or destroyed; it can only be changed from one of form of energy to another form. 

The amount of energy stays the same. 

Describe Conservation of Energy

Click here for more examples of Conservation of Energy:

http://web.singnet.com.sg/~stepchin/Conserv.htm

Remember to hit the “back” button on your browser to return to this slide show.

Section 2: Forms of Energy

• Remember the forms of energy we discussed in section 1? We are going to discuss those even further.

Mechanical Energy

• Mechanical energy is the form of energy associated with the position and motion of an object.

• An object’s mechanical energy is a combination of its potential energy and kinetic energy.

• How do we calculate mechanical energy?Mechanical energy = PE + KE

Thermal Energy

• Thermal energy is the total potential and kinetic energy of the particles in an object.

• If particles have a large amount of kinetic energy, then there is a large amount of thermal energy.

• More kinetic energy = more heat

Electrical Energy

• Electrical energy is the energy of electric charges.

• Electrical energy can be kinetic or potential.

• Example: When you receive a shock from a metal doorknob, lightning, batteries, etc.

Chemical Energy

• Chemical energy is potential energy stored in the chemical bonds that hold chemical compounds together.

• Chemical energy is stored in the foods we eat and even in the cells of our bodies.

• When the bonds are broken, new chemical compounds may form.

Nuclear Energy• Nuclear energy is the energy that is stored

in the nucleus of an atom. It is released during a nuclear reaction.

• Nuclear fission= when a nucleus splits. Nuclear power plants use this to produce electricity.

• Nuclear fusion= when nuclei of atoms fuse or join together. This happens in the sun and releases tremendous amounts of energy.

Electromagnetic Energy

• Electromagnetic energy is light energy. The sunlight that you see each day is electromagnetic energy.

• Electromagnetic energy travels in waves.

• Examples: microwaves, x-rays, UV radiation, radio waves, infrared radiation

Section 3: Energy Transformations and Conservation

Energy Transformations

• Most forms of energy can be transformed into other forms.

• A change from one form of energy to another is called an energy transformation.

• Single transformations: one form of energy is transformed into another form.

• Multiple Transformations: a series of transformations. Example is lighting a candle with a match.

More on Energy Transformations

• Law of Conservation of Energy: Energy cannot be created nor destroyed, only transformed.

• Chemical to electrical transformation: batteries

• Chemical to thermal: food that you eat• Electrical to light: lamp• Electrical to mechanical: plug in drill or fan• Electrical to sound: radio