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Activity: Just Floating Along
Hands-on Exercise: Try this experiment to see why ships needed "ballast." This activity will demonstrate the need for "ballast" in the "hold" of a ship to maintain the ship in an upright position as it travels the seas from port to port.
Materials
- Plastic 1-liter soft drink bottles, or plastic toy boats if desired
- Sturdy scissors that can cut through the plastic bottles
- Containers (large enough that the plastic bottles will fit into lengthwise) filled with water
- Plastic sandwich bags filled with soil, sand or rocks (make the filled plastic bags of various weights)
Instructions
- Cut the plastic bottles in half lengthwise to resemble a boat.
- Place the plastic bottles into the containers filled with water.
- Observe how the plastic bottle floats.
- Place a filled sandwich bag (“ballast”) into the center of the bottle.
- Observe how the bottle floats.
- Place more bags into the bottle until it sinks, making observations on how the bottle floats.
Questions to answer
- Does the bottle sit evenly or unevenly in the water?
- Does adding the filled sandwich bag stabilize the bottle so it floats better?
- Does it matter where you place the sandwich bag in the plastic container? Front? Middle? Back?
- What happens when you place too many bags in the plastic bottle?
Teacher version:
Tramp freighter ship typical of one that may have brought red imported fire ants to the U.S. from Brazil in the 1930's. Courtesy of [http://njscuba.net/artifacts/ship_freighter.html njscuba.net
