Dual-Purpose Unit Demonstrates Collision and Parabolic Trajectories Perform this classic experiment easily with minimal set-up time. The "hunter's gun" is a tube with a spring-loaded launching piston that allows you to adjust the projectile ball's launch angle. The "monkey" is a ball held in place by a battery-powered electromagnet. When you fire the projectile, the electromagnet's circuit is broken; the ball falls and is hit by the projectile. Large, brightly-colored parts make the trajectory easily visible, and an included angle mirror sight speeds the aiming process. The "hunter's gun" has a mounting plate for a table clamp, and it can be used separately as a trajectory apparatus. Includes launcher, electromagnetic free-fall unit, two plastic projectile balls, angle mirror accessory, and complete instructions. Requires support stand and 1.5 V "D" dry cell battery. http://www.cencophysics.com/monkeyandhunterapparatus.aspx