Lesson: Too Much Pressure! Modeling Force-Pressure-Area Relationships

Quick Look

Grade Level: 6 (5-7)

Time Required: 45 minutes

Lesson Dependency: None

Subject Areas: Physical Science

A photograph shows a hand directing a high-pressure stream of water from a hose onto an asphalt road surface. It's a Honda GX160 5.5 HP. pressure washer in action.
Students learn about water pressure.
copyright
Copyright © 2007 Mark Schellhase, Wikimedia Commons CC BY-SA 1.2+ https://commons.wikimedia.org/wiki/File:Pressure_Wash.JPG

Summary

Students learn all about water pressure and how engineers design faucets. Teams build simple systems that model faucets and test them to see the relationships between pressure, area and force. This is a great outdoor activity on a warm day and gives students experience in experimentation, design and teamwork. A student worksheet is provided for guidance and data collection.
This engineering curriculum aligns to Next Generation Science Standards (NGSS).

Engineering Connection

Engineers exploit 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.

Learning Objectives

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.

Educational Standards

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.

NGSS Performance Expectation

3-5-ETS1-1. 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)

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This lesson focuses on the following Three Dimensional Learning aspects of NGSS:
Science & Engineering Practices Disciplinary Core Ideas Crosscutting Concepts
Define a simple design problem that can be solved through the development of an object, tool, process, or system and includes several criteria for success and constraints on materials, time, or cost.

Alignment agreement:

Possible solutions to a problem are limited by available materials and resources (constraints). The success of a designed solution is determined by considering the desired features of a solution (criteria). Different proposals for solutions can be compared on the basis of how well each one meets the specified criteria for success or how well each takes the constraints into account.

Alignment agreement:

People's needs and wants change over time, as do their demands for new and improved technologies.

Alignment agreement:

NGSS Performance Expectation

3-5-ETS1-3. 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)

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This lesson focuses on the following Three Dimensional Learning aspects of NGSS:
Science & Engineering Practices Disciplinary Core Ideas Crosscutting Concepts
Plan and conduct an investigation collaboratively to produce data to serve as the basis for evidence, using fair tests in which variables are controlled and the number of trials considered.

Alignment agreement:

Tests are often designed to identify failure points or difficulties, which suggest the elements of the design that need to be improved.

Alignment agreement:

Different solutions need to be tested in order to determine which of them best solves the problem, given the criteria and the constraints.

Alignment agreement:

  • 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) More Details

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  • Knowledge gained from other fields of study has a direct effect on the development of technological products and systems. (Grades 6 - 8) More Details

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Worksheets and Attachments

Visit [www.teachengineering.org/lessons/view/cub_faucets_lesson1_activity1] to print or download.

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Pre-Req Knowledge

Some knowledge about diameter and area to complete Part 3 of this activity, measurement.

Introduction/Motivation

Have you ever played outside with a garden hose on a warm day? 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.

Assessment

Pre-activity Assessment

Prediction: Ask students to predict the following answers (relationships):

  • How are pressure and height related?
  • How are area and pressure related?

Activity Embedded Assessment

Worksheet: Have students record measurements and follow along with the activity on the Too Much Pressure Worksheet. After the worksheets are completed, have students compare answers with their peers. Review the worksheet 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.

Lesson Extension Activities

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/

Copyright

© 2006 by Regents of the University of Colorado

Contributors

Chris Sheridan; Jackie Sullivan; Malinda Schaefer Zarske; Janet Yowell; Melissa Straten

Supporting Program

Integrated Teaching and Learning Program, College of Engineering, University of Colorado Boulder

Acknowledgements

The contents of this digital library curriculum were developed under grants 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: April 24, 2020

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