Moving water as a Context to Learn Engineering Practices
Introductory Experience: A Simple Water Sprinkler
Experiencing Water Moving in a Circle: The Straw Pump
Construct a simple straw apparatus as follows:
Step 1. Take a wooden BBQ skewer and drive it through the center of a straw. Push the straw to about 1/3 the length of the skewer. Make two small cuts in the straw as shown--but only half-way through the straw. We want it to stay connected, but able to bend.
Step 2. Bend the two ends of the straws down and tape to the skewer as shown. You are now ready to test the pump.Watch the video below to see how to test the pump:
What Engineers Do
How would an engineer look at this little toy? Engineers are problem solvers. For the most part, they work on challenges or issues that need some practical solution. Unlike pure science, engineering seeks a particular solution for a particular problem. Science is more about finding out how and why things work the way they do. Engineers must first have a background in science and mathematics before they can tackle problems.
Think Like an Engineer. Click on the hard hat to read and view about how engineers think, process, and approach challenges.
The Science of the Sprinkler
There are two forces at work here. One, Bernoulli's force which, when the straw spins, air moves over the surface creating a partial vacuum lifting some of the water, and two, the apparent centrifugal force that pulls the water away from the center of rotation.
Consider a pail or bucket attached to a string. You place some water in the bucket. Then carefully you start to spin the bucket in a circle.
After a demonstration of this experiment, there are several observations and questions students may make or could be prompted by the teacher. (It is always a good idea to have students pose their own questions first as most are capable of seeing the issues involved.)
What happens to the water?
What keep the water from falling out?
What forces are acting on the rope? The bucket? The water?
The Bucket on a String with a Hole in the Bottom
Now let's drill a hole in the bottom of the bucket. Let's refill the bucket and try to spin it again. (It is best to do this outside on a piece of concrete so you can see the distribution of the water.)
After the demonstration, students can make observations and again pose questions.
What happens the the water?
What direction does the water want to travel?
Leonard explains centrifugal force.
At this point a general discussion of centripetal and apparent centrifugal forces can be facilitated. Click on the science concept icon for a resource page on this topic.
Keeping Track
Engineers record their work, their thoughts and their observations. It is critical to keep a STEM/Engineering Notebook to track the work in this series of explorations and pattern what we know engineers do. This has great potential to achieve goals in Language Arts as well.
Help students improve their note taking skills and questioning strategies. See the Literacy link: "Taking Notes" and "Generating questions."
Have them take notes and generate questions in their Engineering Notebook.
The notes, observations, and questions posed by the student in the Engineering Notebook can be assessed using a scoring guide or a check sheet.
The Toy Sprinkler: From an Engineering Perspective
So, how would an engineer consider the toy sprinkler knowing something about how and why it works? What problem can they or would they try to solve? We need a context to make this more clear. Why would you need a sprinkler? How could this toy be used or modified to water a garden or larger area?
Essential to an engineering perspective is the reason or challenge that is set. The context, or setting and problem, is an essential launching point for any engineer: Understand the problem, the people, and the environment.
BUILDING SOME BACKGROUND
Once we understand a problem, it is essential we build some background in science, technology and mathematics to help supply ideas to solve the problem. Consider these primitive methods and how they operate as a starting point to the background necessary to move water:
The Shaduf
The Noria
THE TRIPLE BOTTOM LINE
Engineers are challenged to help solve problems. Our context for solving problems is moving water from its source to use for agriculture and human consumption. To solve any of these kinds of problems it is essential to consider the variables that control "how" to solve the problem, what engineers call he triple bottom line.
Engineers will often say that you can't have it be a great design that works perfectly, be the cheapest cost, and fit in with what people want (aesthetics) all at the same time. There are always trade-offs. For example, we could give farmers modern pumps like we use in US agriculture to move water from a river to a field, but in a underdeveloped country, electricity may be unavailable, unreliable or just too expensive for rural folk. Besides, when the pump fails, who will fix it? Finding the right technology for the particular environment and people that is sustainable is the job of an engineer.
Consider the primitive technologies examined above consider the Triple Bottom Line for each. How do they solve the problem, fit into the culture, and are affordable and sustainable? When completed, examine the same TBL and consider how you might alter that thinking for how students would build a model in the classroom. What model would you suggest and why based on your classroom and students' TBL:
1) What materials and design can the students actually build?
2) Cost, materials access, storage, maintenance and use of new materials
3) Ecologically considerate (recycled? easy on plastics?)
Using the materials at hand, build a model for the classroom of one or more of these water moving devices.
ENGINEERING CHALLENGE: Hippo Roller
Lets put our ideas about engineering to work. Consider how engineers approach a problem given certain sideboards or restraints:
Restraints
MAKING A CASE
Once the idea and model are created, the team will make a case. This requires that the idea be put into a logical order of problem solving:
Engineers identify the problem, learn all they can about the people, environment and nature of the problem; the background technologies and science; examine the data; and proposed/brainstorm solutions. Once these are generated and prototypes/sketches and plans are built, the engineering team presents the ideas to the "end users" for consideration and feedback.
SHADUF REVISITED: MATHEMATICS AND PHYSICS FOR ENGINEERS
STEM, especially engineering projects or units, is about how the disciplines have utility in the context of something that is important. We choose the context and the challenge that is meaningful to the culture and environment. In school, this may be a community problem or something the affects the classroom or students directly.
The problem demands that we seek the "advice" of science, technology and mathematics to help engineer the solution. In a way, these disciplines are the handmaidens of engineering. One can pursue STM as a purist, that is we can study these areas and seek to understand how the natural world works without solving any problems. STEM, however seeks to integrate these ideas into a tool kit that helps students understand how these disciplines are needed to address human challenges.
We cannot then just crowbar all the disciplines into each problem and demand that a STEM or engineering unit have an equal amount of each three supportive subjects. We can't go on a "hunt" and force mathematics onto an area that may not naturally lend itself to that discipline. That said, in every engineering challenge, cost and finance are essential elements. Mathematics is always a factor in deciding the efficacy of a project. If we can't afford the solution, then it is no solution at all.
MORE ADVANCED WATER MOVING SYSTEMS
ENGINEERING CHALLENGE
The plunger pump is a simple technology. How could we use this sort of simple technology to help solve a problem for school children in rural Africa?
REVISITING THE SPRINKLER