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The Force of Gravity

The following lesson includes recommendations for adding an additional layer of difficulty for more advanced classes.

Objective: Build a working pump and observe the effect of gravity on water.

Materials: two empty plastic cups; straw; soap dispenser pump; dishpan or other basin; tap water; Archimedes of Syracuse Student Worksheet 2

Time required: 40 minutes

Getting Started:

1. Place two empty cups in a dishpan. Fill one cup with tap water. Give one student a straw and challenge him or her to pour water from one cup into the other through the straw.

2. Ask the observing students to record their observations and provide suggestions for transferring the water through the straw more efficiently. Ask: How much water is “lost” into the basin? How long does it take? (Advanced classes: Ask students to take exact measurements using measuring cups, scales, and a timer. Compare the results of different ideas.)

3. Give students a soap dispenser pump. Ask: How do you think the results will change if we use a pump? (Faster, more efficient)

4. Empty the basin and refill the cups. Use the pump to transfer water from one cup to the other. Record the results.

Using the Student Worksheet:

5. Ask: Where do we use pumps in our everyday lives? (Soap dispensers, plumbing, gas pump, heating systems, home aquariums, your heart, etc.)

6. Distribute copies of Archimedes of Syracuse Student Worksheet 2 and build an Archimedes screw-style pump as a class. Explain that a screw pump is a machine made out of an incline plane. Turning the screw lifts the water up. (Advanced classes: Separate students into teams and have each build their own pump.)


7. Find a water tank on the classroom map. Explain that water is pumped to the top of these towers by many different kinds of pumps. Explain that water tanks are elevated because height impacts pressure. It would take more pressure to pump water to a house that is at the top of a hill than to one at the bottom of the same hill.

8. Ask: If your town was 10 miles wide instead of three miles wide, how could you change your water tank to provide more pressure? (Rebuild on a hill, make it hold more water, make it taller)

9. Build a model water system with your class! Follow the Build a Model Water System instructions within this program and complete Steps 2–6.




Photos: water © Shutterstock

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