In this project named “Catapult”, the materials given are: Popsicle sticks, Plastic spoon, Rubber bands, and Cotton balls. The composition is straightforward by following the simple instructions. Let us have fun and identify the Physics behind each step in the game:)
(1) Set up the composed system as seen in the picture and load a cotton ball on the spoon. The inclined spoon&stick acts like a Lever, the stack of sticks under is the base, and the Pivot is at the midpoint.
(2) Push the open end of spoon and cotton ball together downward firmly! The other end of Lever stick wrapped by rubber band must rise and the rubber band is stretched! The pushing force is doing positive Work and the Elastic potential energy is being raised!
(3) Ready, set, go! Release the spoon&ball! The Lever stick will Rotate about the Pivot point and the Elastic potential energy is transforming to the Kinetic energy!
(4) When the spoon&ball rises to a certain height, the spoon will stop due the constraint of the rubber band, but the cotton ball won’t. Which way does the ball go when leaving the spoon? Newton told us it would go in the Tangential direction of the Rotation circle.
(5) The cotton ball will fly along a pretty curve and finally land on the ground. With the Air Resistance, it is not exactly, but close to a Projectile Motion.
