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Marshmallow Catapult

An image showing seven icy pole sticks wedged between two icy pole sticks secured with rubber bands

This is one pretty sweet catapult that can bend and snap a projectile across the room

Australian Curriculum links

  • Science > Physical Sciences > Year 2 > ACSSU033
  • Science > Physical Sciences > Year 4 > ACSSU076
  • Science > Physical Sciences > Year 7 > ACSSU117
  • Science > Physical Sciences > Year 8 > ACSSU155
  • Science > Physical Sciences > Year 10 > ACSSU190

You’ll need:

  • 9 paddle pop sticks
  • 5 rubber bands
  • A plastic teaspoon
  • Optional: marshmallows (or other objects) to launch!

Try this

  1. Take 7 of the paddle pop sticks and bind them together by winding a rubber band tightly around one end. Repeat this on the other end of the paddle pop sticks
  2. Take the remaining 2 sticks and tie a rubber band on one of the ends. Try to tie the band close to the edge of the sticks.
  3. Gently slide the 7 paddle pop sticks between the 2 paddle pop sticks, splitting the 2 sticks apart.
  4. Loop the rubber band in a cross fashion to join the two pieces together.
  5. Attach the spoon to one of the single sticks using a rubber band to fasten it in place.
  6. Now, place a marshmallow on the spoon, pull back on the spoon and watch your catapult fling!

What’s happening?

The paddle pop stick and plastic spoon have an elastic property, which means they return to their original shape after being bent or deformed. Rubber bands also have this property.

When you bend the paddle pop stick back, you are creating elastic potential energy as the stick and spoon want to return to their original shape. When you release, that potential energy becomes kinetic energy as the catapult and marshmallow start to move.

While the spoon and stick of the catapult stop moving, there is no force to stop your marshmallow and it keeps flying through the air thanks to its momentum.

You can try investigating how far the marshmallow will fly, depending on how far you pull your catapult back. But be careful you don’t pull it back too far!

Real world links

The catapult is just one type of medieval weapon used to fling objects great distances.  Others include the ballista and the trebuchet. Catapults and ballistae store tension in ropes, flexed pieces of wood, or rubber (modern versions only) to launch objects. The trebuchet is different with a pivoting beam and counterweight to help fling objects into the air. All of these were popular during the medieval period in Europe and used in attacks to lay siege on castles and other fortresses. Large catapults can launch projectiles up to 300 m, enabling the attacker to remain at a safe distance.