How can we make a paddle boat?

Make and test a model paddle boat and learn about potential and kinetic energy.

What You Need

• Styrofoam meat tray or baked goods tray (well washed)
• Scissors or utility knife
• Elastic band
• Duct tape

Safety First!

Utility knives are extremely sharp. An adult should be responsible for using this tool.

Never leave a child unattended in a bathtub or near any other body of water.

What To Do

Using scissors or a utility knife, cut the styrofoam tray using the paddle boat part template as a guide.

1. Cut a slit on each side of the paddle boat for the elastic band to be fitted.

2. Loop the elastic band around the paddle end of the boat. The elastic band should easily fit into the slits on the sides of the paddleboat.

3. Place the paddle in between the loop of elastic band. Using small pieces of duct tape, tape the elastic to the paddle on both sides.

4. Wind the paddle towards you while holding the boat part still. Put some water into the sink or bathtub. Carefully place the boat on the surface of the water and let go of the paddle. What happens to the paddle when you let go? What happens to the boat?

As you turn the paddle to wind up the elastic, the elastic gains energy. As the elastic unwinds, the energy makes the paddle turn. When this happens, the flat surfaces of the paddle push the water backward, which causes the boat to move forward.

Everything from clocks to small motors uses springs and elastics to provide them with potential energy. Potential energy is energy that is stored. Stretched or twisted rubber bands and springs can all store elastic potential energy. That potential energy can be converted into kinetic energy (energy of movement), allowing an object like a paddle boat, to move. Similarly, the spring of a pogo stick can be compressed and released, sending the pogo stick upwards into the air!

• Vary the number of turns of the paddle. How does the number of turns affect how far the boat goes?
• Twist the elastic in the opposite direction. Which way does the boat move now?
• Change the size or shape of the paddle. How does the shape effect the movement of the boat?