CBC Archives

Review with the class the method of finding the range and height of a projectile using projectile motion equations, as well as how to calculate the speed of an object by using the conservation of energy law. Explain to the students that they will be building a working model of the supergun. Using elastic bands or springs, they will calculate the speed of the projectile (payload) as it exits the barrel. They will predict the range and maximum height of the payload using projectile motion equations.

Direct students to the topic Dr. Gerald Bull: Scientist, Weapons Maker, Dreamer on the CBC Radio and Television Archives Web site. Have them view Clips #1, 2, and 6, and the Additional Clips “Centennial disgrace” and “Iraq admits to building a supergun,” along with the relevant Did You Know? sections. From these clips students will gather technical information about the gun and its payload. Working in groups of four, they will design and build a scale model of the gun: a projectile launcher powered by a spring or elastic band arrangement. Students will derive the equations needed to determine the range, maximum height, initial and final velocities, and predict the results.

In class or outdoors (depending on the size of the launchers) have students launch their projectiles. Measure the range and angle of elevation of the launch. Have students compare their predicted values of the range to the actual values. Using the actual values, have the students work backwards and calculate the speed of the projectile as it left the barrel. Compare that value to the theoretical value obtained by using the conservation of energy method. Students should try to account for the differences.

Assessment Tip
Make sure students measure in metres and seconds to ensure that Newtons and Joules are consistent.

Students can write a lab report with conclusions.