Simple and compound machines are designed to make work easier. When we encounter a machine that does not fit this understanding, the so-called machine seems absurd. In this lesson, the cartoons of Rube Goldberg are introduced and engage the students in critical thinking about the way his inventions make a simple task even harder to complete. As the final lesson in the simple machines unit, the study of Rube Goldberg machines can help students evaluate the importance and usefulness of the many machines around them.

One engineering challenge is to better society with advances in technology. Many of these greater advances in technology can be seen in machines invented by engineers. Rube Goldberg went to school to be an engineer, and after graduating, he decided to become an artist. He drew cartoons of inventions that did simple things in a very complicated way. His inventions involved many complex systems of simple machines, all organized in a logical row, to accomplish a simple task. An important skill for engineers is to evaluate the design of a machine for its genuine usefulness for its audience. Oftentimes, the best design is the simplest design. compound machines simple machines Rube Goldberg satire work mechanical advantage In order to understand compound machines, it is helpful if the students are familiar with the six individual simple machines and their ability to make work easier, as described in Lesson 1-3 of this unit. After this lesson, students should be able to: Understand why some engineered machines have an unquestionable benefit for society and others do not. Form a critical opinion about the importance of the machines they encounter in life. Explain that mechanical advantage is not always the best way to measure the value of a machine. [Using an overhead or LCD projector, display a transparency or LCD projection of Figure 1, which can be found under attachments.] Let's look at this Rube Goldberg cartoon, the "Self-Operating Napkin." When an engineer designs a machine, she is concerned with how it will fit in with the owner's life or what positive meaning it will have for him. Most often, a machine must be practical in order for it to be used. What's the meaning of the self operating napkin-machine? Let's read through the step-by-step description so we can understand it better. [As a class, read the description: As you raise a spoon of soup (A) to your mouth, it pulls a string (B), thereby jerking a ladle (C), which throws a cracker (D) past a parrot (E). The parrot jumps after the cracker, and the perch (F) tilts, upsetting seeds (G) into a pail (H). The extra weight in the pail pulls a cord (I), which opens and lights an automatic cigar lighter (J), setting off a sky-rocket (K), which causes a sickle (L) to cut string (M), allowing a pendulum with attached napkin to swing back and forth thereby wiping off your chin.] Obviously, the machine is complicated. Would you have been able to decipher all of the steps without the description just by looking at the machine? The simple machines (the ladle, parrot, cigar lighter, etc.) interact with one another in a way that is not immediately apparent, and the end function of the machine is none too obvious either. Until we understand what the machine does, this compound machine remains fairly meaningless—that is, it is really just a funny hat atop a man's head. After we have read the description of the "Self-Operating Napkin," it seems that all the steps fit together, like the different motions within a bicycle, where one simple machine interacts with another to do some end function. Considering that a bike takes us from one point to another, which is quite useful, why wouldn't people find this napkin-machine useful? (Answers should vary. Although the self-operating napkin might make work easier for us by definition, it probably takes more work to merely hold the machine on your head!) [Next, take a look at the "Self-Opening Umbrella."] Do these cartoons remind you of machines or devices in your life? Maybe it reminds you of the new electronically powered transportation device which is supposed to whisk you around a city as you stand or an old camping tent that fits together in a way that still takes forever to figure out. It is easy to see why you would be reminded of these things by the Rube Goldberg cartoons: his images depict machines that do jobs always in the most complicated ways. Can you think of other machines that you have seen that do not have much useful meaning? (Give time for students to answer. Possible example answers: electric eraser, towel warmers, electric can-opener.) Who remembers what the concept of mechanical advantage is? Mechanical advantage is a mathematical expression for how much easier the machine makes work. How do we find the mechanical advantage of a compound machine? Do we simply add the mechanical advantages of each simple machine? No, we multiply the separate mechanical advantages. Engineers use the product of the values of mechanical advantage to explain why a compound machine is many times more useful than a single simple machine. Would these Rube Goldberg inventions have a small or large mechanical advantage? (Answer: probably large, since they involve so many simple machines.) Why are they not realistic for the user? (The machines may be too complex, clunky and weigh a lot to be really useful.) Why is mechanical advantage not always the best way to measure the value of a machine? (In these examples, the added complexity outweighs the need for the machine. The person has to exert more effort to use the machine than is needed for the simple task.) Engineers must have a clear idea about how their machine will benefit people; otherwise, it is unlikely to be used by society. As suggested by the Rube Goldberg cartoons, which seem to exaggerate bad designs, engineers should aim to design machines that fit in well with a person's activities and therefore somehow improve that person's life. In general, the simplest designs are the best. Even in complex machines, the simpler the individual components are, the easier it is to make the machine, and the more reliable it is. Professional engineers aim to do good things for society. Compound machines springing from creative engineering have played an intimate role in people's activities for thousands of years, and since our industrial revolution, this country has seen an explosion in complex machines. Many examples of sophisticated machinery that extend beyond usefulness have opened up during this modern era. Rube Goldberg's (see Figure 3) satirical scope magnifies for us the meaninglessness of some of the machines in our society that have gone far beyond what is useful. Machines — which by definition are to be useful but fail to live up to this standard — are seen as an absurdity in our society. Usually, these machines that do not serve an important purpose are short-lived. Rube Goldberg noticed that ironically these absurd machines were sticking around. Perhaps it was the public's fascination with a new invention, which is undoubtedly exciting, that enabled these machines to linger. Or, perhaps people were effectively convinced by the salesperson that this machine was indeed necessary in their lives. Rube Goldberg desired to document this modern phenomenon and won lasting fame — including a dictionary entry — for his images. Rube Goldberg's cartoons reach to such great heights of exaggeration that we are tempted to look for the meaning: From where do machines in our society grow? Designers and the public alike can see that machines are rooted in serving some real purpose for people. The engineering design of machines must be characterized by a striving for this particular kind of meaning; otherwise, the machine is doomed to an existence as a funny hat or a hunk of material. Consists of two or more simple machines and allows for work to be done easier. The number of times a force exerted on a machine is multiplied by the machine. Cartoonist and engineer who poked fun at overly complicated machines; a machines that operates in a complicated way where the procedure apparently could have been much simpler. The fundamental parts of any machine. Simple machines can exist on their own and are also sometimes hidden in the mechanical devices around you; a device which performs work by increasing or changing the direction of force, making work easier for people to do. Design and Build a Rube Goldberg What is an example of a machine in your life that has positive, useful meaning? (Possible answers: A bicycle, because it fun to ride and it can get you to school; a blender, because you can make delicious smoothies with it; video games, because you look forward to going home and playing them; etc. List the mentioned machines on the board.) Do you think many people have these machines and enjoy them like you do? (The general answer should be yes.) What are some machines you know of that remind you of a Rube Goldberg? (Possible answers: shoes with the blinking lights - the light is useless and annoying; an electric can-opener, because it's not that much easier to use than a manual one; a leaf blower, because it hardly picks up leaves; etc. List answers on board.) The mechanical advantage of simple machines is a numerical representation of how that simple machine makes work easier by actually using the machine. In a compound machine, the mechanical advantages of its individual components are not added together but multiplied, to show a much larger advantage to using multiple simple machines together. In the Rube Goldberg inventions, the mechanical advantage is large, however; the machine makes it very complicated to do a simple task. Remember, these Rube Goldberg designs are intended to make fun of overly complex machines. In reality, engineers must understand their audience in order to design a machine that will fit in well with a person's lifestyle and improve that person's life. : Solicit, integrate and summarize student responses. All ideas should be respectfully heard. Take an uncritical position, encourage wild ideas and discourage criticism of ideas. Ask the students: How many simple machines are contained in the Self-Operating Napkin? (The answer is arguable, but a solid answer is six: the ladle, parrot, perch, lighter, skyrocket/sickle, and pendulum.) If each simple machine had a mechanical advantage of two, what is the mechanical advantage of the compound machine? (Answer: there are 6 simple machines, each with a mechanical advantage of 2, so the total mechanical advantage would be 12.) Encourage Critical Thinking Skills: Lead students in a discussion about the fact that the mechanical advantage of the Self-Operating Napkin is quite high. Ask them: Why is this so? (Answer: Due to the higher number of simple machines together in the compound machine.) Ask them to consider whether or not mechanical advantage is a good way to measure this particular machine's value. Let them talk it over with a neighbor for a minute, and then ask students to share their thoughts. Round Robin Rube: Ask the students to think of a simple task that would make a good Rube Goldberg idea, and raise their hands (or indicate thumbs up) when they have an example. (Possible answers: tying your shoe, raising your hand in class, getting your mail from the mailbox, etc.). Make a list on the board. In small teams or as a class, choose one of the ideas and have one person start the Rube Goldberg design on a piece of paper (or the board) with one simple machine. Have the next student add another simple machine or "step" to design, until everyone has had a chance to add to the design. Discussion Question: Solicit, integrate and summarize student responses. Ask the students to list some complex machines that they have encountered in their lives. Write the list on the board. Have a discussion about the importance of these machines. Do these machines make work easier or harder? How useful are they? Have a discussion about mechanical advantage. Is mechanical advantage always the best way to measure the value of a machine? Why or why not? Have students complete the attached worksheet. This is an exercise in mechanical advantage applied to a Rube Goldberg machine. Have students research inventions that are considered to be Rube Goldberg in nature. http://www.rube-goldberg.com/ Figure 1: Rube Goldberg's Self-Operating Napkin (doc) Figure 1: Rube Goldberg's Self-Operating Napkin (pdf)