This crowd pleasing rocket is easy and cheap to make and investigates the potential energy stored in a rubber band.
Warning: This activity involves a flying projectile. Even made of soft foam, it could cause eye injuries. Don't fire it at people or animals.
You will need
A heavy rubber band - you can buy these from a newsagency.
20 cm of foam insulation tube - you can buy this cheaply from hardware stores.
A cable-tie
Stiff cardboard
Scissors
Sticky tape
What to do
With the scissors, cut about two centimetres from the end of the foam insulation tube. Put this aside for the time being - this small band will add a bit of weight to the nose of your rocket and softens its impact.
Tie the cable-tie around the foam tube about one centimetre in from an end, making sure the rubber band is looped inside. Pull the cable-tie as tight as possible (maybe you could get somebody with a strong arm to help you with this).
Clip off the loose end of the cable-tie.
Slip the small piece of foam tubing you cut off in step 1 over the cable-tie to hide any sharp edges.
Now for the fins! Cut three slits in the other end of the rocket, running about a quarter of the length of the tube. Each slit should be evenly placed around the rocket tube.
To make the tail fins, cut three right angled triangles from a piece of card with one straight side about 12 cm in length.
Sticky-tape all three fins together by their 12 cm straight sides so they are able to stand up on their own.
Trim the corners from the fins, then cover the outer edges with sticky tape for added strength and to smooth the edges.
Slot the fins into the end of the rocket; one fin into each slot. When you're happy with the positioning, hold it in place with sticky tape.
Your rocket is ready to launch! Find an open space away from people or objects that could be broken. Hold the end of the rocket with one hand and slip the loop of the rubber band over the end of your thumb on the other (giving the 'thumbs up' before you launch).
Stretch the rubber band while holding the rocket steady and close to your body as your arm extends away from you.
Let go of the rocket.
Practice and see how far you can get your rocket to launch by stretching the rubber band more or less - this determines how much energy you give the rocket
What's happening?
How does the simple elastic band work? The rubber is made of plastic. All plastics are polymers, from the Greek words 'poly' for many and 'meros' for unit. As the name implies, plastics are made up of long chains of repeating chemical units, each bound together.
In some plastics, these chains are stuck to one another, making the plastic stiff and hard. In others, the chains are free to slide about, allowing the substance to flow and change shape.
In rubber, the chains of units are coiled tight and the bonds between them are loose and can be separated over a distance .
Stretching a rubber band uncoils the polymer chains. Feel a rubber band after stretching it about ten times. Does it feel warm? Uncoiling the chains makes them produce heat energy. When you let go of a stretched rubber band, the bonds pull the chains back into coils and the band returns to its original shape.
This is all a matter of energy!
Energy is something like the Universe's currency. It makes things happen. We see it work in different forms; such as light radiation, sound, and heat. Kinetic energy is the type we see when objects move, such as your rubber band rocket in flight.
Where does the energy come from? The Law of Conservation of Energy says energy cannot be created or destroyed, however it can be transferred and often changes forms in the transferral. It can also be stored as potential energy, as in rubber bands.
The more stretched a rubber band is, the more potential energy it has. When it is let go, the potential energy rapidly turns back into kinetic (moving) energy, launching the rocket. You'll notice the more stretched the band is, the further the rocket travels; more potential energy means more kinetic energy.
Applications
The same properties that allow your rubber band rocket to launch are also used in many other applications, such as hand-spears for fishing, slingshots and even bungee jumping.
Thinking more broadly, hydropower, a form of renewable energy, relies on the potential energy of water stored in rivers and dams stored above sea level. The potential energy of water changes into kinetic energy when the stored water flows down through channels to turn the blades of a turbine to generate electricity.
Tie the cable-tie around the foam tube about one centimetre in from an end.
Cut three slits in the other end of the rocket, running about a quarter of the length of the tube. Each slit should be evenly placed around the rocket tube.
Sticky-tape all three fins together by their 12 cm straight sides so they are able to stand up on their own.
Hold the end of the rocket with one hand and slip the loop of the rubber band over the end of your thumb on the other.
The rubber is made of plastic. All plastics are polymers.
