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Target Practice


Build a catapult using a lever, and power it with a rubber band. Then, use what you've learned to build your own design, and send a marshmallow flying through the air!

  • Target Age: 6-10
  • Skills/Subjects: Science
  • Related Episode: Episode 402: Don't Like Fencing? Try Fencing!

WHAT TO DO

1.Get what you need:

  • plastic spoons
  • rubber bands
  • duct tape
  • craft sticks
  • brass fasteners
  • mini marshmallows
  • scissors
  • pen
  • toilet paper or paper towel tubes
  • cardboard base (chipboard, shoebox, tissue box, cereal box, milk carton, etc.)
  • target (trash bin, for example)
  • meter stick (optional – for Dig Deeper activity at bottom of page)

2. Construct a catapult.

  • Attach a toilet paper tube to a cardboard base. This is your fulcrum.
  • Tape the handle of a plastic spoon to the end of a craft stick. This is your lever.
  • Use a pen to make a hole in the top of the tube and insert the lever. Secure with tape.
  • Punch a hole in the base in front of the tube (using the pen), and attach a brass fastener.
  • Wrap a rubber band around the brass fastener, then around the middle of the lever (so that there is tension as you pull it back). Tape in place.

Two toilet paper tube kazoos covered in tin foil and waxed paper.

 

 

3. Launch it! Pull back on the lever and put a marshmallow on the spoon. Then, let go! What happened?

4. Design Your Own. Now that you know how to build one kind of catapult, brainstorm your own design. Try a different base or fulcrum, build a different type of lever, or use the rubber band in a different way.

5. Test it! Can your marshmallow hit a target? How can you make it go farther? Or higher? Change one thing (a variable), like the length of the rubber band or the position of the lever. Predict what will happen. Then, test it!

CHEW ON THIS!

A catapult is a device used to hurl an object. It uses a simple machine called a lever (the spoon and craft stick), which is attached to a stationary point called a fulcrum (the cardboard tube), to help move a load (the marshmallow).

Your catapult is powered by the rubber band. When you pull back on the lever, potential energy is stored in the rubber band. When you let go, the potential energy is transferred to the lever and turned into the energy of motion (or kinetic energy), and the marshmallow is flung forward.

DIG DEEPER!

  • Catapult contest! See whose catapult can send the marshmallow the farthest. Use a meter stick to measure the distance, and then record the results.
  • Pop Fly. Make a lever and send a ping-pong ball flying high! Check it out at Design Squad.

DID YOU KNOW?

The catapult was used in ancient and medieval warfare to hurl stones and other projectiles at the enemy. Today, catapults are used for other purposes – like launching airplanes into the air! Ships that carry aircraft don't have space for long runways, so planes need help getting airborne. An aircraft catapult slings a plane forward, helping create enough lift for a safe takeoff.

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