The trick is WHAT you sling. Hard ammo is prohibited in public, but try slinging tennis or golf balls and you can say it's a sport.
How can we find the "mouth" of a sling, to calculate it's "energy at mouth" ? I'm pretty sure tennis balls are crappy ammo from a power stand point.
Edit : without ammo, a sling is a strap, a belt or whatever you want :p You can even use it as a coat hanger to free your hands
La pierre d'achoppement est le projectile. Tirer des balles en terre, du plomb ou des caillasses est interdit en public en effet. Merci de me l'apprendre, je tâcherai de ne pas me faire prendre la prochaine fois que je tente de remplir l'étang d'à côté.
Mais des balles de golf ou de tennis devraient passer non ? comment on trouve la bouche d'une fronde ? Pour calculer l'énergie à la bouche
Note : only bilingual people will be able to follow my way of thinking... good luck, i even lost myself, too late for me now :p