High school students learn about two-dimensional motion, arc, velocity and magnitude while completing construction of a catapult for physics class. Students should draw simple designs and select inexpensive materials that are easy to replace. Physics teachers often conduct a competition to see whose catapult is most effective, so discuss what projectiles you will launch, such as eggs or marshmallows, and practice measuring the catapult's lauch ability and object's distance in order to adjust your design as needed to improve efficiency.
- Skill level:
- Moderately Easy
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Things you need
- 1/2-inch PVC pipe
- Mitre saw
- 2-inch hinge
- 1/2-inch PVC tee joints
- 1/2-inch PVC elbow joints
- Rubber bands
- Plastic bowl
Cut PVC pipe into two 3-inch parts, six 6-inch pieces, four 12-inch sections, two 15-inch pipes, and a 21-inch section.
Connect an elbow joint on each end of a 6-inch PVC section. Screw a hinge onto the centre of the 6-inch piece and attach the 21-inch section to the hinge arm to create the catapult arm. Insert 12-inch pieces into the open elbow ends to create a W-shape.
Insert a tee joint on the end of each 12-inch piece. Attach a 6-inch section on the opposite end of each joint, and place a 12-inch section into the end of the tee. Place an elbow joint on each upright 12-inch piece so the open ends face each other and connect with a 6-inch section. This will stop the catapult arm after it is released.
Place tee joints on the exposed ends of the 6-inch pieces in the catapult base. Insert 3-inch pieces in the opposite slots and mount a 15-inch piece in the leg of the tee. Connect the two 15-inch sections with elbow joints and a 6-inch PVC bridge, replicating the arm stop created in the previous step. This structure is called the helper.
Attach elbow joints to the open end of the 3-inch sections and complete the base by inserting a 6-inch piece into the elbow joints.
Place two rubber bands together and loop two more rubber bands around them, resembling a + shape. Create four identical rubber band sets and loop the ends of the rubber bands around each corner of the helper and the arm stop.
Complete the catapult by adding a seat for the projectile. Attach a small plastic bowl to the launch end of the catapult arm by drilling a hole in the base of the bowl and driving a screw through the bowl into the pipe.
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