TEACHER:

Lory Heron, physics
Procter Hug High School
Reno, Nevada

AGES:

Seven to 12

PROJECT:

Build a catapult

GOAL:

To test the relationship between the angle of release and the distance traveled by a catapulted object

Reno residents know Lory Heron as the Pumpkin Lady. For the past nine years, her physics students have participated in the annual pumpkin-toss contest to see who can construct the catapult that will make a pumpkin travel farthest. The incredibly popular event drew about 1,500 enthusiastic spectators last year. "It gets students thinking about a basic physics principle," says Heron, who teaches tenth through twelfth graders. Specifically, it introduces them to the world of vectors.

Two-dimensional vectors are diagrammatically represented as two arrows beginning from the same point, one traveling horizontally and the other vertically. They offer a way to organize information about how objects move through space. "Kids learn that you want your pumpkin to not only go up but out for maximum distance," says Heron.

Heron has seen students construct catapults out of wood and springs, make giant slingshots from plastic pipe and rubber bands, and fashion crossbows from car springs. One girl rigged her bicycle with a 14-foot arm attached to her back axle. The arm held the pumpkin until the girl stopped the bike, triggering the pumpkin's flight. "This is the kind of creative thinking and problem-solving that kids don't often get to do," says Heron.



MATERIALS
• Wood block, 2 by 2 inches
• Paint stick or wooden ruler
• Plastic spoon
• Plastic mailing tape
• Marshmallows
• Pencil and paper
• Protractor

INSTRUCTIONS
1. Construct your catapult by placing the wooden block flush with the top of the paint stick. Then lay the handle of the spoon on top of the wooden block with the bowl of the spoon extended over the paint stick. Again, the spoon handle should be flush with the edge of the block. Lash the three pieces together with plastic mailing tape.

2. Place the free end of the paint stick next to the wall. Load the marshmallow in the spoon, pull it down as close as you can to the paint stick and prepare for liftoff.

3. Release the spoon and watch your marshmallow soar. Then measure the distance from the wall to where it lands. This is the distance covered using a 90-degree angle. Record your distance and angle on a sheet of paper.

4. Now use the protractor to measure 10 degrees off the floor. Lift the end of the ruler to that height. Reload your spoon, release and record the distance using an 80-degree angle.

5. Repeat this procedure for different heights. Then review your written results and figure out which angle worked best.