?
WHAT’S HAPPENING
The catapult works like this: When you pull
back the throwing arm, the two ends of the
cord wind around the reel and tighten up.
Because they are not stretchy, they pull
the plastic arms of the catapult
downward with them. Then when you let
go of the throwing arm, the tension arc
springs back to its “relaxed” position
again. The faster that happens, the more
momentum your paper “coconut” has
when it’s launched.
REMEMBER
You have just converted energy! When you t
ension the arc
by pulling back the throwing arm, the c
atapult stores
energy. When you let go of the arm, the st
ored energy is
converted into the energy of motion (kinetic ener
gy). There
are many different kinds of energy, s
uch as mechanical,
electrical, and chemical energy. Ener
gy can be stored or
converted but it can’t be used up. This is c
alled the law of
Conservation of Energy.
6
5
Now cross the ends of the string over each
other and tie them firmly onto the hooks on
the tension arc.
6
Pull back the throwing arm to tension the
catapult. As soon as you let go, the throwing
arm shoots forward.
Tip!
5
Don’t fire anything except smal
l paper balls
with your catapult. Crumple up pie
ces of
(brown) paper — about the siz
e of this note
— into pellets and see if you c
an hit
the monkey on the elastic bel
t pulley.
4
25
Coconut Catapult
