# Weird Science: How to create a mini submarine - Hawaii News Now - KGMB and KHNL

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### Weird Science: How to create a mini submarine

(HawaiiNewsNow) - D-4, you sunk my battleship! But don't worry, Dr. V is here. He's going to tell us about submarines, and show us how they work.

Things you need:

• 1 clean 16 or 20oz. water/soda bottle
• Metal skewer or power drill
• Bendy straw or tubing
• Pennies
• Aluminum foil
• Tape
• 3 wide rubber bands
• Large tub of water

The experiment

Please ask an adult for assistance with using the power drill or skewer.  Drill three holes along the side of the soda bottle, evenly spaced from the top to the bottom. Drill a hole in the cover of the bottle just big enough to put the straw or tubing in. Stack the pennies into three piles containing 4, 8, and 12 pennies and wrap each pile in foil. Place a rubber band around the plastic bottle and slide it next to the closest hole. Position the other rubber bands next to the two remaining holes. Place the four-penny stack under the rubber band closest to the bottle's top. Place the eight-penny stack under the middle rubber band, next to the middle hole. Place the 12-penny stack under the last rubber band (NOTE: The weights should be next to the holes NOT over them.) Push the shorter end of the straw or tubing (about 1 inch) through the hole in the bottle's cap. Reattach the bottle cap to the bottle. Tape the straw or tubing securely into place on the bottle cap. Lower your "submarine" into the water making sure you don't let the tube or straw take in water. What happens to your submarine? What happens when you blow into the straw or tubing? How well does your submarine work? What happens when you change the penny weights?

How does it work?

Your submarine simulates how a real submarine works. A submarine can control its buoyancy, or the weight of the water it displaces. To control its buoyancy, a submarine has ballast tanks that can be filled with either air or water. When the submarine is at the surface of the water, the ballast tanks are filled with air, making the submarine's overall density less than that of the surrounding water, like when you blow air into your bottle. When the submarine dives, the ballast tanks are filled with water until its density is greater than the surrounding water (negative buoyancy), and it begins to sink, like when your bottle fills up with water. In a submarine, the ballast tanks are spaced throughout the submarine so the angle of the dive or surface can be controlled.

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