In my physics were making siege machines so my partner and I made a giant crossbow, instead of the bow's arch doing the pulling work we used a big rubber band. Unfortunately this works pretty bad barely getting 30 ft so I wanted to know if anybody had any ideas to launch a tennis ball down the crossbow's guide (a stronger elastic, magnets, Ect) any help would be super appreciated ! via /r/DIY http://ift.tt/2rfM1rM
