Students are introduced to the structure, function and purpose of locks and dams, which involves an introduction to Pascal's law, water pressure and gravity.
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- Colorado: Science
- 8. changes in speed or direction of motion are caused by forces (Grades 3 - 5)  ...show
- Common Core State Standards for Mathematics: Math
- International Technology and Engineering Educators Association: Technology
- F. Knowledge gained from other fields of study has a direct effect on the development of technological products and systems. (Grades 6 - 8)  ...show
- E. The design and construction of structures for service or convenience have evolved from the development of techniques for measurement, controlling systems, and the understanding of spatial relationships. (Grades 6 - 8)  ...show
- Next Generation Science Standards: Science
- Define the criteria and constraints of a design problem with sufficient precision to ensure a successful solution, taking into account relevant scientific principles and potential impacts on people and the natural environment that may limit possible solutions. (Grades 6 - 8)  ...show
- Explain the basic operation of a dam and lock system.
- Know that dam and lock system are used to aid in river navigation.
- Know that engineers use Pascal's law when designing dam and lock systems.
Lesson Background and Concepts for Teachers
|dam:||A barrier to obstruct the flow of water, especially one made of earth, rock, masonry and/or concrete, built across a stream or river.|
|engineer:||A person who applies her/his understanding of science and mathematics to creating things for the benefit of humanity and our world.|
|gravity:||An invisible force of a mass being attracted to another mass. For example, the Earth's mass pulls you down so you stay on the ground instead of flying away.|
|lock:||An enclosed chamber in a waterway with watertight gates at each end, for raising or lowering vessels from one water level to another by admitting or releasing water.|
|Pascal's law :||A hydrostatics principle that says that for all points at the same absolute height in a body of a fluid, the pressure is the same, even if additional pressure is applied on the fluid at some place.|
|pressure:||The exertion of force upon a surface by an object, fluid, etc., in contact with it. Expressed as force per unit area.|
- Under Pressure - Students use plastic soda bottles filled with water to learn about Pascal's law and water pressure. Observing how water spills from holes punctured at different locations, they learn and how water exerts equal pressure in all directions, and how water at increasing depths is under increasing pressure.
- How does it feel to dive to the bottom of a swimming pool?
- Does the water feel "heavier"?
- Do your ears sometimes hurt when you dive down too deep?
- What if you dive even deeper into a lake or an ocean?
- Why is the water pressure 5 meters beneath the surface half as great as it is 10 meters beneath the surface? (Answer: Water pressure comes from the weight of the water above, so at 10 meters, twice as much water is above than at five meters. Height, not length or width, is what matters for determining water pressure. Use Pascal's Law with the h = 5 m and h=10m to obtain pressures of 49,050 N/m^2 and 98,100N/m^2 , respectively. Have students note that the pressure for 10 meters is twice that for 5 meters.)
- How does gravity help a boat get across a dam and lock system? (Answer: Gravity "moves" river water in and out of the locks. Water is drained [by gravity] from the first lock until it is even with the second lock. When the water levels are even, the vessel can move into the lower lock).
- Why are dam and lock systems important for our economy? (Answer: Locks enable large boats to travel up and down rivers much further than they could travel naturally. They also enable boats to navigate through shallow or steep sections of river. With this travel improvement, merchants can ship products and good longer distances, increasing the global market.)
Lesson Summary Assessment
- What is the purpose of a dam and lock system? (Answer: To raise and lower boats between stretches of water of different levels on waterways.)
- How is gravity involved in dam and lock systems? (Answer: Gravity is a factor in how boats move through dam and lock systems by how it moves and drains water, which raises and lowers the boats in the locks.)
- In what situations might construction of a lock improve river or canal navigation? (Possible answers: Locks help commercial boats and barges navigate past sandbars, rapids, waterfalls, temporarily low water, changing riverbed elevations and dams.)
- If we didn't have dam and lock systems, how might we move boats through these waterway obstacles? (Possible answer: We could design and build boat lifts, and some places have boat lifts. But, locks make more sense for big ships [imagine cruise ships, ocean tankers, cargo ships] and barges; locks let water and gravity do the heavy work of moving the vessels.)
- What must engineers consider about water pressure so the dam and lock systems they design are safe, strong and reliable? (Answer: As the elevation of water behind a dam increases, its height and density causes increasingly high pressure at the bottom of the dam. Water pressure also affects the walls and gates of locks. Engineers must estimate and take this pressure under consideration in order to make dam and lock structures watertight and strong enough to stand up to the water pressure forces.)
Lesson Extension Activities
Additional Multimedia Support
Adler, Jerry "Troubled Waters. The Great Flood of '93 Rolled Inexorably Down the Mississippi, Teaching Everyone—Even Television Anchormen—Never to Underestimate Nature." Newsweek. Published July 26, 1993, pp. 66-80.
Ardley, Neil. How "We Build Dams." Ada, OK: Garrett Educational Corporation, 1990.
Cannelton Locks and Dams. Perry County, Indiana, http://www.perrycountyindiana.org/attractions/canneltonlocks.cfm, accessed July 14, 2009.
Dictionary.com. Lexico Publishing Group, LLC., http://www.dictionary.com, accessed July 14, 2009. (Source of some vocabulary definitions, with some adaptation)
Kagan, Spencer. Cooperative Learning. Capistrano, CA: Kagan Cooperative Learning, 1994.
Lock and Dam 6, Trempealeau, WI. Updated September 26, 2007. US Army Corps of Engineers. Accessed July 14, 2009. http://www.mvp.usace.army.mil/
Locks and Dams. 2006. Newton's Apple Teacher Guides. KTCA Twin Cities Public Television, http://www.newtonsapple.tv/TeacherGuide.php?id=1041, accessed July 14, 2009.
Locks and Dams: How do locks and dams work? How does a lock and dam make an unnavigable part of a waterway navigable? Newton's Apple Insights. KTCA Twin Cities Public Television, http://www.darylscience.com/Demos/Lock-Dams.html, accessed July 28, 2009.
Nelson, S.B. "Water engineering." In Standard Handbook for Civil Engineers. Edited by F.S. Merritt. New York: McGraw-Hill Companies, 1983.
Old Man River. St. Paul, MN: U.S. Army Corps of Engineers, 1988.
Skorupa, Joe. "The Problem with Dams." Popular Mechanics. Published December 1991, pp. 106-107.
Jeff Lyng, Kristin Field, Denali Lander, Lauren Cooper, Denise W. Carlson
© 2008 by Regents of the University of Colorado.
Integrated Teaching and Learning Program, College of Engineering, University of Colorado Boulder
Last modified: March 27, 2015