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Home School Life Journal ........... Ceramics by Katie Bergenholtz
"Let us strive to make each moment beautiful."
Saint Francis DeSales

Building Lab, Part 8: Dams and Water Pressure


Water pressure increases with the depth of the water. In deep water, there is more water "piled up," which causes the pressure to be greater at the bottom than at the surface. A dam's design must enable it to withstand greater pressure at the bottom than at the top. As a result, many dams are built in a triangular shape. The wide bottom withstands the great load of the water deep below the surface, while the top of the dam can be built thinner so as not to use unnecessary costly materials.


Water squirts further at greater depths
For greater details on this demonstration, see School for Champions

Demonstration

Poke three holes in the side of a milk carton and cover them with a single strip of tape. Fill the carton with water. Hold the carton with one hand and quickly pull off the tape. The water will stream out of each hole with different force. Explain that water behind a dam is a live load pressing on the dam. The greater the amount of water built up, the greater the pressure–so the water coming from the bottom hole has more force than the water from the top hole.

Brainstorm

Water discharging from the bottom of a dam has great force. Have your students brainstorm ways in which to release the pressure and have them illustrate their ideas. They may suggest using multiple spouts, a triangular spout to release the water, or using a "diffuser", which is a structure that is used to break the stream of water, sometimes as simple as just a mass of large boulders.

Build a Dam
You are part of a team of engineers given the challenge of building a system to dam up 5 liters of water in a classroom trough. You'll have lots of materials to use such as cardboard, pvc pipes, tape, foil, plastic wrap, cups, straws, paper clips, wooden dowels, cotton balls, plastic sheets, clothes pins, wire, string, screen, fabric, springs, other readily available materials. You have a base of gravel at the bottom of the trough which simulated the rocky or sandy bottom of a river bed. You'll need to not only stop the water, but develop a system so that you can release a little at a time in a controlled way. You'll need to stop the water, let a little come through, and stop it again. Plan and build a dam model, using the instructions found at Try Engineering. 

1 comment:

  1. I like the demonstration. It shows what you're teaching really well.

    Every time it rains and we get a flood in our backyard, the kids try to build a dam in a section of our yard to stop the water flow.

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