energy

common
common peeps i really need ur help

gunpowder.

aviation fuel.

muscle power (think baseball or boomerang or spear).

rubber bands (slingshot, in America--I think the Brits call them catapaults--as in your other thread).

lever extension of an arm--atlatl spear.

the classic sling--like David and Goliath--a long band of cloth or lever, with a pouch for a projectile in the middle. You hold either end of the band, swing it around to build up speed, and let go of one end of the band, so the projectile flies out--needs much more practice than a slingshot.

Look at medieval siege engines, used in warfare to fling heavy projectiles before gunpowder--kinetic energy stored in twisted bands; lever arms with a heavy weight on a short arm dropping down and flinging up the longer arm with a lighter weight on the end of it into a long arcing flight, and for that matter giant bows.

And of course bows, stretching a limber material (the bow, which springs back into its original shape, and propels the arrow as it does.

but really you should do your own homework rather than relying on us to get intrigued by the question.

thanx for the help and just to let u know
all i needed was a couple of names of things to get me started u dont understand i have been searching the net looking up sorts of stuff to help me and u wouldnt belive the crap that comes up TOTALLY USELESS