SummaryIn this activity, students learn how engineers design faucets. Students learn about water pressure by building a simple system to model faucets and test the relationship between pressure, area and force. This is a great outdoor activity on a warm day.
Engineers use the relationships between, pressure, force, area and work when designing different mechanical and fluid systems. Fluid systems may include the piping system in and throughout a single building or a whole city water system. The design of pumps and valves for the piping system include pressure and work calculations. Another example that uses the concepts of fluid and mechanical systems is the heating and ventilation system in a building — a damper in an air duct acts like a valve in a piping system, but for air instead of water.
The students must have some knowledge about diameter and area to complete Part 3 of this activity, measurement.
After this activity, students should be able to:
- Explain how water pressure changes with height.
- Describe how the area of an opening affects the force of water flow.
- Design and evaluate a model faucet.
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Each TeachEngineering lesson or activity is correlated to one or more K-12 science,
technology, engineering or math (STEM) educational standards.
All 100,000+ K-12 STEM standards covered in TeachEngineering are collected, maintained and packaged by the Achievement Standards Network (ASN),
a project of D2L (www.achievementstandards.org).
In the ASN, standards are hierarchically structured: first by source; e.g., by state; within source by type; e.g., science or mathematics;
within type by subtype, then by grade, etc.
Each TeachEngineering lesson or activity is correlated to one or more K-12 science, technology, engineering or math (STEM) educational standards.
All 100,000+ K-12 STEM standards covered in TeachEngineering are collected, maintained and packaged by the Achievement Standards Network (ASN), a project of D2L (www.achievementstandards.org).
In the ASN, standards are hierarchically structured: first by source; e.g., by state; within source by type; e.g., science or mathematics; within type by subtype, then by grade, etc.
- Define a simple design problem reflecting a need or a want that includes specified criteria for success and constraints on materials, time, or cost. (Grades 3 - 5) Details... View more aligned curriculum... Do you agree with this alignment? Thanks for your feedback!
- Plan and carry out fair tests in which variables are controlled and failure points are considered to identify aspects of a model or prototype that can be improved. (Grades 3 - 5) Details... View more aligned curriculum... Do you agree with this alignment? Thanks for your feedback!
- Know the formulas for the area and circumference of a circle and use them to solve problems; give an informal derivation of the relationship between the circumference and area of a circle. (Grade 7) Details... View more aligned curriculum... Do you agree with this alignment? Thanks for your feedback!
- Add, subtract, multiply, and divide decimals to hundredths. (Grade 5) Details... View more aligned curriculum... Do you agree with this alignment? Thanks for your feedback!
- Develop and apply formulas and procedures for area of plane figures. (Grade 6) Details... View more aligned curriculum... Do you agree with this alignment? Thanks for your feedback!
Each group needs:
- 2-3 empty plastic 10-16 oz bottles
- 2-3 2-foot sections of plastic tubing of varying diameters
- 3 feet of duct tape
- One bucket or catch basin
- One gallon of water
- Corks or rubber stoppers
- 1 copy of the Too Much Pressure Worksheet
Have you ever played outside on a warm day with a garden hose? What happens to the flow of water when you bend the hose in half? (Answer: The water stops flowing.) What happens when you put your finger over the end of the hose? (Answer: The water sprays or the water flow stops.) Sometimes you can get the water in the hose to come out in a small stream, but then this stream comes out faster and the water shoots farther across the yard. Why is that? It happens because the smaller opening increases the velocity (speed) and pressure of the water coming out of the hose.
What happens when you swim in the deep end of a pool? What happens as you go deeper and deeper in the pool? Your ears may begin to hurt. In fact, your ears hurt because of the pressure of the water. How do you think water pressure and depth is related? (Have students discuss the answer with the person sitting next to them and then discuss their answers as a class.) The deeper you go the more pressure there is and the more your ears hurt. The same thing is true for air pressure (another fluid) and height. The higher in the air you go, the more pressure you feel in your ears.
These things are determined by the properties of fluid flow (in these examples, air and water). Fluid flow and fluid properties are concepts that engineers need to know about when designing a many things, including the water plumbing for our houses, buildings and schools, etc. Engineers need to think about how water is going to get through pipes, and ultimately to our sinks. They need to think about how to get enough pressure for the water to flow through the pipes and the faucets, so we can wash our hands or get a drink of water.
Today we are going to experiment with some of the properties of fluid flow. We are going to play with water, do some measurements, and think like an engineer to use what we learned in designing a faucet.
The measurement portion of this activity is modeled after the following equation:
Q = V*A
where Q = flow (ft^3/min or gallons/minute), V = Velocity (ft/min), and A = Area (ft^2)
For example, as your thumb decreases the area across the tube (kind of like closing a valve at the end of the tube), per the equation above, a decrease in area results in a higher velocity, assuming the flow stays the same. It is similar to putting your thumb over the end of a garden hose to get it to spray further. Assuming the flow is constant, a decrease in area results in a higher velocity of the fluid so that it shoots further out, or puts more pressure on your thumb.
Before the Activity
- A week prior to activity tell students to bring in 3 empty plastic soda bottles.
- Assemble supplies for each group.
- Cut bottom ends off of bottles. (Note: You may decide to include this for the students to do in step 1 of the Assembly.)
With the Students
- Assemble students in groups of two.
- Distribute supplies and a Too Much Pressure Worksheet to each group.
- Let students know that today they are going to be engineers who are trying to figure out the best design for a faucet.
Part 1: Assembly
- Have students assemble the pressure testing device as follows. (Student assembly instructions are also provided on the worksheet.)
- Insert plastic tubing about one inch into the top of a bottle (as shown in Figure 1).
- Wrap duct tape around the tube and bottle top in order to form a watertight seal, as shown in Figure 2.
- One student should hold her thumb securely over the end of the tube.
- Hold the device over the catch basin, the second student should fill the bottle about ¾ with water.
- Still over the catch basin, hold the bottle two feet above the end of the tube (where you thumb is stopping the water at the end of the tube), as illustrated in Figure 3.
Part 2: Experiment
- Have the students follow the steps of the experiment and answer the corresponding questions on their Too Much Pressure Worksheet.
Part 3: Measurement
- Students should measure the diameter and area of the tubes in their experiment and record their answers on their worksheet. Note: the worksheet requires the students to calculate the area of each tube. In the interest of time, this step can be skipped and the teacher can provide the area of each tube.
- Have students repeat the steps of the experiment with the next two different bottles.
Part 4: Engineering Design
- Have students think about their experiment and measurement. How can they use what they learned to design a faucet? Allow students to use available supplies (corks, stoppers, tape, anything else) to make the final part of their faucet, which will ultimately control the water flow. Have them draw their design on the worksheet.
Remind students to be careful with the water and not let it splash anywhere but into the catch basin.
In order to see a difference in the force for different areas, water pressure must be kept the same. This is maintained by making sure to hold the plastic bottles up such that the top water line is always at approximately the same height.
Prediction: Ask students to predict the following:
- How pressure and height are related.
- How area and pressure are related.
Activity Embedded Assessment
Too Much Pressure Worksheet: Have the students record measurements and follow along with the activity on their worksheet. After students have finished their worksheet, have them compare answers with their peers; review their answers to gauge their mastery of the subject.
Post Activity Assessment
Worksheet Discussion: Review and discuss the worksheet answers with the entire class. Use the answers to gauge students' mastery of the subject.
Prediction Analysis: Have students compare their initial predictions with their test results, as recorded on the worksheets. Ask the students to explain how pressure, area and height are related.
Show and Tell: Have the students "show and tell" to the rest of the class the faucet designs they created, explaining their work to the other students.
As a class, generate a list of a few characteristics of water on the board or someplace where everyone can see them. Then, ask the students to think of a common item that an engineer designed with that fluid property in mind. Examples of fluid characteristics might include that water flow increases with height or depth, water force increases with smaller opening, that water has to be held together in a container, etc.
Have the students think about the pressure in a water column. How much pressure is there at the deepest point in the ocean, the Mariana trench? First, find the depth of the trench and use the hydrostatic pressure gradient equation to calculate the pressure ( ). Research the answer at http://www.marianatrench.com/
For younger students, the activity can be done without calculating the area and giving more specific instructions.
ContributorsChris Sheridan, Jackie Sullivan, Malinda Schaefer Zarske, Janet Yowell, Melissa Straten
Copyright© 2006 by Regents of the University of Colorado.
Supporting ProgramIntegrated Teaching and Learning Program, College of Engineering, University of Colorado Boulder
The contents of this digital library curriculum were developed under a grant from the Fund for the Improvement of Postsecondary Education (FIPSE), U.S. Department of Education and National Science Foundation GK-12 grant no. 0338326. However, these contents do not necessarily represent the policies of the Department of Education or National Science Foundation, and you should not assume endorsement by the federal government.
Last modified: July 5, 2017