Here is a fun idea for older girls or build one as a team. Science and fun meet with Punkin Chunkin challenges. The idea is simple — create a machine using any materials you can find and see who can send a pumpkin the farthest. Expect a mess. Simplify it with mini pumpkins for younger girls.
Punkin Chunkers have a few options when it comes to streaking the skies with squash. All are based on the concept of force, power, and torque:
Any machine using compressed air to launch a pumpkin is called an air cannon. Air is compressed into a tank. When the constraint holding the air is removed, air expands back to its normal volume. The result is released air acts like a spring and forces the pumpkin through the tube at great volume, blowing the pumpkin out.
A catapult machine uses stretched springs or rubber bands, which store energy. When the springs or bands are pulled and then released, the stored up energy is transferred to the arm of the device, which hurls the pumpkin.
A torsion machine is any device that uses twisted rope as its primary source of power. It relies on a rope that works by torsion or twisting. The rope stores mechanical energy when it is twisted. The amount of force it releases is proportional to the amount it is twisted.
Any machine with an arm that spins at least 360 degrees to launch a pumpkin is known as a centrifugal. The basic idea in a centrifugal is to accelerate a pumpkin by spinning it in a circle many times, with each rotation gaining more and more momentum until it can build up enough energy to propel the pumpkin forward.
The basic idea of a trebuchet is to transform the potential energy stored in the lifted heavy mass into the kinetic energy that is the motion of the smaller mass (the pumpkin). It uses a short arm, which is weighted down with a heavy object to counterbalance against the long arm, where the projectile (the pumpkin) is placed. When the heavy mass of the short arm falls down, it provides energy to fling the long arm.