August 17th, 2016

In this section you will find information about the content that is featured throughout the unit. You can use the information to refresh your memory or
as a reference when questions about energy arise in your classroom. The vocabulary in the lessons is described in simple terms for use with middle school students who are just starting to explore complex physics ideas. Students will learn more detailed information about this same content and the calculations behind the concepts in later grades. For now we suggest focusing on the simplified ideas as a way to introduce the content to your students.

## 3.0 — Energy: Background Content and Teacher Information

### Content Information

There are many different kinds of energy. When something has energy, it means it can make things happen or “do work.” The more energy something has, the more change it can create.

Think of a bowling ball hitting pins at the end of the bowling lane. If the bowling ball is moving slowly, it is unlikely that it will result in much change to the bowling pins. However, if the bowling ball is moving fast, it will create a greater change to the pins by knocking them all down.

When mentioning energy students may be more familiar with some types of energy, than others. Here are brief explanations of some different types of energy:

• Thermal energy is directly related to temperature and increases as temperature increases. (E.g. A cup of hot tea has more thermal energy than a glass of iced tea.)
• Light energy can come from the sun (or another light source) and causes a change in temperature when adsorbed. (E.g. light shining on a black car in the summer causes the outside of the car to be hot when touched.)
• Chemical energy is stored in the bonds between atoms and molecules (e.g. when you eat a piece of candy, your body breaks down the sugar and other chemicals, to provide energy to your body).

Energy can be transferred and change forms. These changes in energy indicate that there was an interaction between objects. For example, there is a transfer of thermal energy from the pan to the pancake batter when you cook a pancake. Later when you eat the pancake, the flour, eggs and sugar that were combined to make it contain chemical energy.  The chemical energy stored in the pancake by its ingredients is broken down by your body to provide energy for you to move, think and grow.

This unit focuses on kinetic and potential energy because these are the two types of energy shown in the Playground Physics app.

Kinetic Energy (KE)

Any object that is moving has kinetic energy. If an object is not moving, it does not have kinetic energy. The kinetic energy of an object is dependent on the mass and speed of the object. Kinetic energy increases as the speed of an object increases and as the mass of the object increases. In summary, potential energy depends on an object’s speed and mass.

Potential Energy (PE)

Objects that are still also have energy. This energy, called potential energy, can come from different sources. Objects can have chemical potential energy due to the energy stored in the chemical bonds. When the bonds are broken, energy is released. Potential energy can also come from the position of the object.

Objects can have gravitational potential energy as a result of its vertical position. The higher the object is above the ground, the more potential energy it has.

*Note – The Playground Physics app shows potential energy in relation to vertical position. It is important to remember that what you are really seeing is gravitational potential energy, even though it is simply called “potential energy” in the app.

### Patterns of Energy: Swinging

Many of the lessons in this unit revolve around the physical activity of swinging. These lessons focus on noticing the movement of the person swinging, describing the energy involved in the motion of swinging, and looking for the patterns in the energy of the person swinging. Below are some of the patterns your students may notice about the energy involved with swinging.

• The potential energy of the person swinging increases as they get further from the ground.
• The potential energy of the person swinging is at a maximum when the person is furthest from the ground.
• Kinetic energy increases as the speed of the swinger increases.
• The kinetic energy of the swinger is at a maximum when the person is moving the fastest. This happens at the bottom or apex of the arch of motion of the swing.

If your class does not have access to swings, the activities in this lesson can also be done by creating pendulums in the classroom and using Playground Physics to analyze the energy of the pendulum. The patterns in energy will be the same for a person as a swing as they will for a pendulum.

### Common Misconceptions

• Students often believe that living and moving things have energy but inanimate objects and things at rest do not have energy. Even if the object is inanimate and not in motion, the object can have potential energy simply due to its position in relation to its surroundings.
• At times students use the words “force” and “energy” interchangeably. When students do so it can be helpful to ask them to explain what they mean by using more common language to get at the core of the idea or thought they are trying to describe.
• Students often think that objects cannot have kinetic energy and potential energy at the same time. Objects can have both kinetic and potential energy at the same time.

Conservation of Energy

The Law of Conservation of Energy states that energy cannot be created or destroyed, only converted from one form of energy to another.

Apps used
Duration: 0-20 mins
Prep: Easy
Categories: Energy, How-to, Play, Practices

#### Learning Objectives

3.1 Swinging Part I

3.2 Fun with Energy

3.3 Swinging Part II

3.4 Swinging Part III

3.5 Four Corners

3.6 Odd One Out

3.7 Swinging Higher

#### Vocabulary

• Speed is how fast an object is moving regardless of its direction.
• Kinetic energy (KE) is the energy of an object in motion.
• Potential energy (PE) is stored energy that an object has as a result of its vertical position.