Make a trebuchet that throws tennis balls.

Trebuchet and Ballista pictures. Tennis balls. Pre-made throwing arm with small round plastic tub attached to hold the projectile. 12 x 1 mtr hazel poles with pointed ends per trebuchet, Shock cords, twine, rubber mallets, tent pegs, ball of twine, scissors (teacher use only), masking tape.

Share what we know about siege engines. Study pictures of trebuchets.

 Safety. Hazard can arise out of the failure of the trebuchet framework under load so make sure it is completely rigid before use. It is also vital that when in use all present stand a safe distance behind the trebuchet. Safety can be enhanced by attaching a cord to the top of the throwing arm and using this to pull back and release the throwing arm. When dismantling always remove the throwing arm first.

Making. Two tripods are made 40cms apart and firmly braced together by tying two poles 30cms and 65cms from the ground. Add rigidity by using twine to make guy ropes to the front, rear and sides. Next, add the shock cords. Position them between 15cms and 20cms from the top of the tripods.  Twist the shock cords together to create extra tension. Tie the throwing arm firmly to the shock cords or feed it between the twisted cords. Tie the end of the throwing arm firmly to the lower bar.