Energy Learning Community

Bouncing Back - The Energy of a Bouncing Ball

Grade Level:

Introductory Physics (Grade 9)

State Standards:

  1. 2.1
    Interpret and provide examples that illustrate the law of conservation of energy.

  2. 2.2
    Interpret and provide examples of how energy can be converted from gravitational potential energy to kinetic energy and vice versa.

Lesson Question:

What types of energy conversion are there when a ball is dropped and it bounces back up?

Is energy conserved?


Why haven't we built a machine that can swing back and forth indefinitely?

When I drop a tennis ball, why doesn't it bounce back to the height it was dropped from?

Why do bumper cars ricochet off each other but actual cars tend to crumple in on one another?

The answers to all of these questions are related.

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

We often talk about losing energy, or wasting energy, but where does it go?

Is it really gone forever, or is it just hard to track down?

In the following lesson, we will examine the law of conservation of energy, and try to figure out what happens to energy as it is transferred from one form to another.


Lesson Experiences:


Day 1: Introduction to Conservation of Energy (Elicit and Engage)

  1. Opener:
    Students answer the following question in their log book:
    • Will the Newton’s cradle (shown below) ever stop moving? Why or why not? (5 mins)
    Students will think-pair-share their responses for the class.
    Newton's Cradle animation

  2. Watch Bill Nye video on conservation of energy with bowling ball pendulum. (3 mins)

  3. Students are given a lecture about Gravitational Potential Energy, Kinetic Energy, and Conservation of Energy.

Day 2: Inquiry Activity


Day 3: Glogster Evaluation and Extension

You and your partners will create a Glogster that will be evaluated on the following criteria:

  1. Definitions of the terms:
    • gravitational potential energy
    • kinetic energy
    • conservation of energy

  2. Explanation of the energy transfers involved in dropping and bouncing a ball.

  3. Photo/video documentation of your bouncing ball investigation.

  4. Calculations of
    • initial potential energy
    • final potential energy
    • and "efficiency" of one of the balls bounced in the lab

  5. A video from the web of energy being converted from one from to another form or forms.
    You must state:
    • An estimate of how much energy the process begins with.
    • How much energy is lost, if any.
    • What form or forms the other energy is converted to.

  6. Your Glogster should be colorful and creative.


At this point you should be able to describe:

While we have looked at simplistic forms of this in class, like bouncing balls, we can apply this to almost any other aspect of energy transfer in the real world.

How does bouncing a ball relate to operating a flash light?

Is energy conserved when we pop popcorn? If not, where does it go?

Assessment Rubric

You will be able to....
Strong Good Adequate Adequate Weighting
Energy Check on ClassMarker All answers complete and calculated correctly. All answers complete and calculated correctly. 3/7 answers correct and complete. 0-3 answers correct and complete. 10%
LabData Sheet Data sheet is neatly filled in with multiple trials for three different balls.
All calculations complete and correct.
Analysis questions complete and correct.
Data sheet is filled in with sufficient objects and trials.
Some calculations incomplete or incorrect.
Some analysis questions incomplete or correct.
Data sheet has insufficient objects or trials.
Most calculations incomplete or incorrect.
Most analysis questions incomplete or incorrect.
Data sheet is not complete.
No complete or correct calculations.
No complete or correct analysis.
Energy Worksheet for Homework Worksheet is entirely complete worksheet is mostly complete worksheet is half complete worksheet is less than half complete 10%
Glogster Has accurate definitions.
Explains energy transfer during bouncing ball in detail.
Includes documentation of lab investigation.
Shows calculations of one ball from the lab.
Includes video and analysis of another example of energy conversion.
Is neat, colorful, and creative.
Glogster contains 4-5 of the required elements. Glogster contains 2-3 required elements. Glogster contains less than 2 of the required elements. 40%
Participation in discussions
and on task behavior
Always participatory and on task. Mostly participatory and on task Sometimes participatory and on task. Rarely participatory and on task. 20%



Balls of various weights and sizes, meter sticks, gram scale, digital camera/video recorder, 8 laptops.

Book: Hsu, Tom. CPO Phyics: A First Course

Classmarker:Energy Check