Break It Down!

What You Need


In addition to the following materials, you may also encourage students to bring materials from home.

  • Poster paper
  • Pens
  • Pencils
  • Markers
  • Cardboard
  • Scissors
  • Tape
  • Rubber bands
  • Paper clips
  • Glue
  • Tooth picks
  • Plastic
  • Pieces of wood
  • Twine
  • Marbles
Break It Down!


To explore the everyday implications of system failure and to challenge students to identify the causes of system failure.


There are two prerequisite lessons for this lesson: Systems 1: Simple Machines and Systems 2: Systems, Up, Up and Away! In the first lesson, students observe the interaction of parts and establish a framework for understanding "system." In the second lesson, students explore how changing parts or amounts of parts can impact the properties of a system. This lesson asks students to further their experience by exploring the everyday impacts of system failure and challenges them to identify the causes of failure.

At this grade level, students should become more comfortable with developing designs and analyzing product improvements. They should begin to enjoy challenges that require them to clarify a problem, generate criteria for an acceptable solution, suggest possible solutions, try one out, and then make adjustments or start over with a newly proposed solution. (Benchmarks for Science Literacy, p. 49.)

Students should also learn that technologies always have side effects and that all technological systems can fail. These ideas can be introduced in simple form early and gradually become more prominent in the upper grades. (Benchmarks for Science Literacy, p. 48.) Students should also be able to understand that a system or device may fail for different reasons: because some part fails, because some part is not well matched to some other, or because the design of the system is not adequate for all the conditions under which it is used. Other reasons include over-design and redundancy. (Science for All Americans, pp. 31–32.)

This lesson will go further in helping to dispel the common misconception among children that the properties of a system belong to its individual parts rather than to the interaction of its parts. (Benchmarks for Science Literacy, pp. 262–263.)

Planning Ahead

These ScienceNetLinks lessons are prerequisites for this lesson:

For the Motivation section: Provide students with a number of simple and compound machines like the ones listed below. Since the lesson focus will be on system failure, include among these a few machines that do not work. This could be done by removing a key part.

  • Inclined plane
  • Wedge
  • Screw
  • Lever
  • Pulley
  • Wheel and axel
  • Corkscrew
  • Doorknob
  • Eggbeater
  • Bottle opener

For the Development section: Provide students with at least three sets of machines that can be found around the classroom. Here are some examples:

  • Two staplers—one that works, one without staples
  • Two pencil sharpeners—one the works, one that is missing a part or not plugged in
  • Two clocks—one that works, one that is not plugged in or wound up
  • Two pens—one that works, one that has run out of ink
  • Two flashlights—one that works, one without batteries

Important note: Prior to the lesson, place the "broken" machines around the class for students to discover on their own.


To spark interest in the subject and to review what students learned in the two prerequisite systems lessons, provide students with a number of simple and compound machines to touch, look at, and talk about. Be sure to include among the machines one or two that are broken or do not work well. This will help to draw students' attention to system failure—the main focus of this lesson—and faciliate discussion of the topic. Here are some sample discusson questions:

  • What kind of machine do you have?
  • Is it a simple or compound machine? Why?
  • What kind of parts does it have?
  • What do you think this machine is used for?
  • Why do you think people make or use machines?

At some point during this exploration, a student may comment that one of the machines is not working properly. Allow this likely development to lead the class into a discussion of system failue (and their past experiences with machines that have failed). Guiding questions may include:

  • How do you know when a machine is working properly? Offer examples.
  • What happens when a machine fails? Offer examples.
  • What kinds of things cause machines to fail? Offer examples.
  • Have you ever had a machine at home that didn't work? Offer examples.
  • What do you think caused this to happen?
  • What effect did this have on you or your family?
  • What did you or your family do about this situation?

Help students see that all machines, whether simple or complex, can fail. When this happens, there are real-life consequences. Machines can fail due to poor product design, poorly built or connected parts, poor maintenance, or other causes. Inform the class that they will learn more about why machines sometimes fail, and how redesigning the parts of a machine might help it function more effectively. Because people's lives are so dependent on well-functioning machines, this information has important real-life applications.


Extend students' ideas about system failure by drawing their attention to the set of "broken" machines that you placed around the classroom prior to the lesson. This can be done by pointing to, for example, the broken clock (which is stuck at 6:00 p.m.) and asking someone to tell you what time it is. You can also ask a student to sharpen one of your pencils using the broken sharpener. Another could try to staple some papers for you using a stapler without staples. In each scenerio, you may ask basic discussion questions such as:

  • What's the matter?
  • What might be causing it not to work?
  • When a machine like this doesn't work, what can we do about it?

After each of these discoveries, retrieve the "broken" machines and place them on a table with, for example, another clock, pencil sharpener, and stapler that work properly. Invite students to compare the machines and try to determine why one of the pair is working and the other isn't. General guiding questions may include:

  • Why do you think this machine is working and the other is not?
  • Are all of the parts working?
  • What do you think it would take to fix this machine?

Once students have determined the cause of the malfunction(s), provide them with the missing parts or opportunty to get the machines working again. When all the machines are working properly, ask questions such as:

  • What would happen if we could not fix this machine?
  • What would happen if we only had one of them and it didn't work?
  • How might this situation affect our day?

Then, as a way to prepare students for the online activity, pick up one of the machines—like a stapler—and have a simple discussion about cause and effect and the difference between the individual parts and the system parts. Guiding questions may include:

  • What does this stapler do?
  • What would happen if this [random] part were missing? Would it work? Why or why not?
  • Are there any parts on this machine that I can take off and it would still work properly?
  • Imagine for a moment that you didn't have a stapler, but needed to attach several pieces of paper together. What are some simple ways you could do this?

Explain to students that they will now have the opportunity to look at a machine and see how its parts work individually and as part of a larger system. Some of the parts will be necessary for the machine to function, while others will not. In some cases, fewer parts will actually help the machine work better.

Now have students use their Break It Down! student esheets to visit the Break It Down! interactive, in which they observe, explore, and manipulate a machine—or system—made up of ramps, switches, levers, and gears. Marbles roll through the system and eventually hit a lever attached to a flagpole on the right side of the system. Each time the marble hits the lever, the flag goes up. If the flag falls all the way to the bottom, the system has broken down. The purpose of this activity is to remove as many parts of the system as possible while keeping the flag from falling all the way to the bottom.

As students look over the system, have them discuss what they see happening. Then have them read the "Learn More" section, which provides them with background information about systems, followed by the "How to Play" section. As they are reading, ask students to be prepared to answer these comprehension questions (you may want to have students record their responses so that they will remember them for the discussion):

  • What is the object of the game?
  • What happens when the system works?
  • How do you know when the system is broken?

Make sure students understand that the object of this activity consists of keeping the system working with the minimum number of parts.

When students begin to explore and manipulate the system on their own, encourage them to remove some parts of the system by clicking on the blocks and see what happens. Then have them discuss what they have observed, by answering questions such as:

  • What kinds of parts make up this system?
  • What do the parts do individually?
  • What do these parts do together?

After more observation, exploration, and manipulation of the system, have students address issues concerning system failure and possible improvements in system functioning. Ask questions such as:

  • What happens when the system is working?
  • What happens when the system fails?
  • What are the different ways it can fail?
  • What parts are necessary for this system to work well?
  • What parts are not necessary?
  • Does taking away unnecessary parts make the system work better or worse? Explain.
  • What happens when the system works better?

Encourage students to experiment and discover the arrangement of parts that makes the system work best.

Next, students will have the chance to apply what they have learned by creating their own simple, motion-based machines like the one in the previous activity. Have students use their student esheets to visit Motion Machine from the Science Museum of Minnesota, where they will learn about how one 4th-grade class built simple machines that make at least one motion.

Note: This activity may be stretched over a two- to three-day period, allowing time for design sketching, machine development, and final class demonstrations/presentations.

First, have students look at photos and descriptions of each of the machines and design processes. While looking through the sample machines, have the class focus on one or two and address questions such as:

  • What is the purpose of this machine?
  • What kinds of parts are used?
  • How do the parts work together?
  • In what ways could this system fail?
  • Do all the parts seem necessary for the system to function?

Next, divide the class into pairs or groups. Inform each group that they will be expected to build their own unique machines that use at least one motion. Then present their choice of building materials, so that they can plan, think about, and design a machine according to what will be available to them. Perhaps they could have a choice as to when they sketch. Some groups may want to sketch before they build, while others (who process less abstractly) may benefit from sketching what they have built once they are done.

During the design and building phases of these projects, each group will be expected to rework and redesign their systems so they: can be built effectively; work efficiently; have minimal chances for failure; and include no unnecessary parts.


Once the groups have finished the design and building phases of their projects, have them complete the Build It Up! student sheet, which can serve as a basis for their machine presentations/demonstrations.

Finally, have the groups present and demonstrate their machines to the class. Encourage observers to ask questions about the difficulties each group faced and what they learned during each phase of the development process.


For related Science NetLinks lessons, see:

Other online resources from the Science Museum of Minnesota include a collection of Air-powered Machines and Zoo Machines that can both inspire and challenge students to learn about, sketch, and/or create these types of more complex and imaginary machines.

Students may enjoy the challenge of exploring and identifying over 50 "super simple" to "hideously hard" machines throughout a home and barn by visiting EdHead's resource, Simple Machines. This site features numerous animations, quizzes, and other interesting resources.

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Lesson Details

Grades Themes Type Project 2061 Benchmarks