Things You will Need
- A sheet of cardboard or Styrofoam
- Liquid dishwashing soap
- Dropper or Pencil
How to Make
- Cut a sheet of cardboard into the shape of a boat; it should be 2 inches long and 1.5 inches.
- Make a triangular shaped notch in its back (as shown in the figure).
- Place your boat in a water tub, so that your boat has enough space to move.
- Place a drop of liquid dishwashing soap in the notch of your boat with dropper or pencil.
Now, watch your boat going around the tub! It will move forward.
How it Works?
Water molecules are attracted to each other, which creates surface tension in the water. Liquid dishwashing soap is a surfactant; it breaks down the surface tension of water. When you add liquid dishwashing soap in the notch, it breaks the surface tension of water inside the notch. As a result, it creates enough force to push the boat forward. We have used light material (e.g. Styrofoam or cardboard) to build the boat. Because, light materials can be easily pushed when surface tension breaks.
- Use different materials to build your boat and find out! Which material provides more speed?
- Can you rotate your boat without moving it forward or backward? Think about it.