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How Many Licks Does it take to get to the center of a Tootsie Roll Pop

How Many Licks Does it take to get to the center of a Tootsie Roll Pop

Author: Brian Lien

The objective of this lab is to teach students about mechanical engineering.

They will learn how to measure gear ratios, calculate gear tains, and measure gear torque. Once they learn how to do this, they will create a machine using gears and a counter to lick a Tootsie Pop. At the conclusion of the

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Rubric for the machine

Team member’s ______________________, __________________________


Grade Rubric How Many Licks


Design and build a machine to answer the question, “How many licks does it take to get to the center of a Tootsie Roll Pop?”


1. Identify the Problem/Product Innovation:

25 _____ Preparing a clear definition of the problem. (pg. 329 stage 1)

25 _____ Listing the constraints or limitations that the solution must meet. (pg. 329 stage 2)


2. Investigate issues related to the problem by:

20 _____ Looking in stores and catalogs to find how other people solved similar problems (competitive analysis).

30 _____ Prepare sketches or make photocopies of what you find.


3. Develop several solutions (Brainstorming) to the problem by:

20 ea 100 total_____ 5 Different Design Solutions

100 ea 500 total _____ Quality of Sketching

50 _____ Highlighting ideas that you think could be used for your final design.


4. Evaluate – Analyze Potential Solutions:

20 _____ Listing the strengths of the design.

20 _____ Listing the weakness of each design.

20 _____ Selecting the best design.


5. Make a sketch and dimensional  CAD drawing of the solution you have selected for the design problem.

50 _____ Include the sketch in your design portfolio.

50 _____ Prepare a list of materials, supplies, and tools that you will need to make the selected design.


6. Implementing your design

200 _____ Build your machine and test the functionality.

If you have flaws with your design, you must return to step 4 and redesign until your machine works.


7. Evaluate your design by:

33 ea 100 total_____ Conducting the tests. 5 test runs needed.

20 _____ Describing how your machine functioned during the testing.

20 _____ Did you have to redesign? Explain in portfolio

50 _____ Summarizing the results of the test.





8. Functionality

100 _____ Your solution fulfilled its intended purpose of 5 trials without redesign between trials. Trials must be at school and 2 of them on video.

9. Safety

100 _____ Your design must be safe to operate and will not spray water when in operation or leak water when sitting or in operation. You did not destroy any of the material in the box I provided for you.

10. Ergonomics

100 _____ Your machine’s counter is easy to read while the machine is in operation.


11. Appearance

100 _____ The appeal of your product is based on your selection of materials, processes,   finish, color and shape. You should use color representation of Tootsie Pop material and/or paint the project except the box material supplies.

12. Economics

100 _____ Your product was produced with a minimal of extra money yet still is attractive in design. 



Team Total Correct ________/1650

Presentation Rubric for Tootsie Pop Machine

Name ______________________________

Name ______________________________



Tootsie Roll PowerPoint

Grading Rubric


                   Your PowerPoint must include:


25 _____ Introduction slide.

20 _____ Overview of presentation

25 _____ Identify the Problem/Product Innovation

20 _____ Investigate issues related to the problem

10 _____ Pictures of other projects like this (not to include projects from PHS)

50 _____ Take us through the design process

50 _____ 5 sketches

20 _____ 1 refined sketch

30 _____ Final drawing

50 _____ Why did you choose this design

15 _____ Pictures of your final design

20 _____ Implementing your design

50 _____ Results of your machine

30 _____ 3 or more Pictures showing your final design at work

50 _____ Evaluate your design by

20 _____ Describe how your machine functioned during the testing

20 _____ Did you have to redesign

10 _____ What went well in the process (from beginning during gear practice till the end

10 _____ What would you do differently in the future (when in a group and on your machine

20 ____ What would you do next time to improve your machine even further

10 ____ 3-5 minutes

25 ____ Slides easy to read

10 ____ Background of slides appropriate

30 ____ Each member participated equally

30 ____ Use of Props

50 ____ Presentation well rehearsed with smooth delivery that holds audience attention.

50 (25 ea) ____ Dress Professional each person

50 (25 ea) _____ Talks to the audience not the screen.

50 (25 ea) _____ Watch you body language (hands, moving back and forth)

50 (25 ea) _____ Voice (not monotone, loud enough for all to hear)

30 _____ Ready on time

20 _____ Mechanics (no spelling errors)


_______ / 950 possible

(Turn in a copy of you presentation 1 day before your presentation)



Lesson Plan for Tootsie Pop Licking Machine

Getting to the Center of a Tootsie Roll Pop

Brian Lien


PrincetonHigh School is relatively large, urban, four-year comprehensive high school that serves approximately 2,000 students in Cincinnati, Ohio. Academic offerings include, among others, the International Baccalaureate program, technology, business, and general studies. Approximately 82% of the graduates attend college, with 60% going to four-year schools and 22% enrolling in two year/technical schools.

Before utilizing the “Tootsie Pop Challenge” in a new engineering class next year, I tested it with four engineering drafting students. It was quite successful and the students had a great time.


You are assigned the task of helping the Tootsie Roll Company to answer the age old question—how many licks does it take to get to the center of a Tootsie Roll Pop? Students can use any means available to complete the challenge, including viewing the following Tootsie Roll-related websites at


How many licks does it take to get to the center of a Tootsie Roll Pop? This was the question I posed to my engineering drafting class. None of the students had ever worked on a problem-solving activity like this. They all planned to go into engineering at the university level next year and wanted a challenging project that was not drafting-related.


The original idea came from a cooking show, but I wanted to make a lab out of it. The first step was to ask the students to do some research to determine if an answer even existed. After consulting the Tootsie Roll website, they discovered that engineering students at Purdue University had worked on the problem. They saw an example of the machine used by the Purdue students, and then began the design process working on a solution of their own.

Engineering Discipline(s)

Since my students had no experience with different engineering fields, I explained to them they would be working on the study of mechanical engineering. One of my first tasks was to teach them about gears and gear ratios. Your students may also discover the involvement of some chemical engineering. As the Tootsie Roll Pop gets smaller, you will need to figure out, “why?” If your results are anything like ours, the sugar build-up on the “tongue” material will become saturated and then the design may begin to fail, necessitating a project redesign .



For this lab, I found that we used the following standards:

  1. Students will develop an understanding of the attributes of design. (Standard 8)
  2. The design process includes, defining a problem, brainstorming, researching ideas, identifying criteria and specifying constraints, exploring possibilities, selecting an approach, developing a design proposal, making a model or prototype, testing and evaluating the design using specifications, refining the design, creating or making it, and communication the process and results (Benchmark H)
  3. Design problems are seldom presented in a clearly defined form.

       (Benchmark I)

  1. The design needs to be continually checked and critiqued, and the ideas of the design must be redefined and improved. (Benchmark J)
  2. Requirements of a design, such as criteria, constraints, and efficiency, sometimes compete with each other. (Benchmark K)


  1. The student will develop an understanding of engineering design (Standard 9)
  2. Engineering design is influenced by personal characteristics, such as creativity, resourcefulness, and the ability to visualize and think abstractly. (Benchmarks J)
  3. A prototype is a working model used to test a design concept by making actual observations and necessary adjustments. (Benchmarks K)
  4. The process of engineering design takes into account a number of factors. (Benchmarks L)


  1. Apply the design process (Standard 11)
  2. Identify the design problem to solve and decide whether or not to address it. (Benchmarks M)
  3. Identify criteria and constraints and determine how these will affect the design process. (Benchmarks N)
  4. Refine a design by using prototypes and modeling to ensure quality, efficiency, and productivity of the final product. (Benchmarks O)
  5. Evaluate the design solution using conceptual, physical, and mathematical models at various intervals of the design process in order to check for proper design and to note areas where improvements are needed. (Benchmarks P)
  6. Develop and produce a product or system using a design process. (Benchmarks Q)
  7. Evaluate final solutions and communicate observation, processes, and results of the entire design process, using verbal, graphic, quantitative, virtual, and written means, in addition to three dimensional models.


Lab  Objectives:

  1. You will be able to build a machine that will answer the question from above.
  2. You will be able to explain how gear ratios work and why it is important for this lab.
  3. You will be able to explain how the Tootsie Roll Pop got smaller. Was it friction, dissolving product, etc?
  4. You need to write up your conclusions in a paragraph. You must use data from at least three or more test runs from your machine.
  5. You must keep a log of your time spent on each part of the design process.
  6. Write a conclusion and evaluation of your end product.


Teacher Preparation

The amount of preparation depends upon the labs you have. I had to gather material and machines the students will need to solve the problem. I did not want my students gathering stuff for this lab. However, if you are incorporating this into a class that involved this type of work, your students could gather materials on their own or from your classroom supplies. I used the gears from the materials provided from the Society of Automotive Engineers A World in Motion II Design Challenge 2. Other materials you will need are:  materials the students can use for tongues like sponges or paper towels, scrap wood for the frame of the project, small fasteners, and, of course, plenty of Tootsie Roll Pops.

After you or your students have the materials, you must teach the design process. My students knew nothing about the design process so I introduced the problem to them and gave them the problem statement “How many licks does it take to get to the center of a Tootsie Roll Pop?” Once they understood what the problem was, they began investigating previous attempts to solve the problem. This is where they found out what other schools had done. They also found solutions to the problem on the Tootsie Roll website.

The students began to formulate their own solutions based on the materials they had to use. They began with sketches then started to rough out their solutions using the parts and the scrap wood I gave them. After inventorying the available materials, students realized they would have to refine their sketches. Once they had an idea they thought would work, they began making a prototype. This stage took the longest. None of them had ever worked with saws or drills, which meant that it was necessary for me to teach them tool safety before allowing them to work with the tools to finish their prototype.

Lastly, students tested and evaluated the product. Both groups found flaws in their designs and had to modify at least twice from what they thought would be their final design. Once they had a good working model, they tested the solution to the problem. One group found out that it took about 535 licks and the other group found out it took 1200 licks. After they did their testing I brought both groups together to see why there was such a large difference in the data. They discovered that the licking surface area of the two devices was very different. One had a large area, while the other was barely making contact with the Tootsie Roll Pop. This prompted the engineering students to try to figure out the mathematical difference in the surface area of the tongue from one group to the other. The final step was to write the lab up and discuss their findings.

Content Outline

The content outline is intended to organize teaching strategies to allow students to reach an intended outcome. This is the information I wanted my students to be able to do.

A. Impacts of products/systems

  1. Collection of information
    1. The students must test the machine at least three times and keep the results in a chart form. They should keep the Tootsie Roll Pops after they are finished so you can take a picture of it and then measure the diameter of each pop to see if there are any differences.
  2. Evaluation of collected information
    1. They need to write a paragraph about how they think the Tootsie Roll Pop got smaller. Was it dissolved by the water, friction from the tongue, and the Pop? If there were difference, why?
    2. They must keep a log of the design process. They must include who is doing what and for what period of time.
    3. Write an evaluation of your design and what you might do differently if you reworked the solution again.


Activities/Case Studies

This is the first time I have tried this lab. The final determination of the lab design is up to each group of two students. They must look at their research and then discuss how they are going to build the lab.

The actual time to make the project and test the machine was two weeks. I had another group of students from a different class at the same time. It could probably be done in as few as five to seven days if enough dedicated time was available.



Following completion of the lab class work, students should assess their work. This assessment will be based on the successful completion of building the machine and the write up of the lab. They must include the data from at least three tests as well as their conclusion as to what process or processes made the candy disappear. They must also include an explanation of how they followed the design process and what each partner did during each part of the process. Finally there must be a summary of the process, problems encountered, and what would they do again if they had a chance to rework the process.



Pictures of previous attempts—both successful and unsuccessful.

A website about how gears work.


This lesson plan layout came from: Once you are there, navigate your way to



My students had a great time designing this project and I have taken the two machines to two different exhibits. I have had engineers see the lab and think it looks like a very fun lab to discover the concepts of mechanical engineering.


Brian Lienis a technology teacher at Princeton High School in Cincinnati, Ohio. He can be reached via email at