One type of catapult experiment teaches students about the importance of tension. Give each group of students four different materials to use as their catapult: a rubber band, a long piece of paper, a piece of spandex and some putty. Have the students use each material to launch a penny as far across the classroom as possible. The rubber band will launch the penny much farther than any other substance. Discuss with the class afterward how the rubber band is so much more effective because of its much higher tension.
Have students bring their catapults to class along with a variety of objects, each with different mass. For example, you could bring a paper clip, tennis ball, baseball and a nickel. Launch each object from the catapult and have the students determine how far each object traveled. Use this experiment to help the class understand that an object that is very heavy will travel a shorter distance than a very light object if those two objects are pushed with the same force.
Build a small model wall made of Lincoln logs or a similar material. Use a small model catapult to launch a variety of objects at the wall. Have students explain why some objects, such as a ball of paper, do not break the wall, or why some objects, such as a rock, break the wall. The basic conclusion of the lesson is that objects with greater mass hit the wall with more energy, thus causing more damage.
Have the students bring their catapults outside along with an object, such as a ping pong ball. Try to use the catapult to launch the ball as high in the air as possible. Hold the catapult at different angles to see how the angle affects how high in the air the ball is launched. During class discussion, help students understand how the launch angle determines how far the object will travel horizontally or vertically.