Modelová Otázka ID 2678 - 
Dělová koule o hmotnosti 4 kg je vystřelena kolmo vzhůru do výšky 405 m. Jak dlouho bude při zanedbání odporu vzduchu trvat, než po dosažení nejvyššího bodu trajektorie dopadne zpět do místa výstřelu?
Správná odpověď je: B
Doba, po kterou koule z nejvyššího bodu trajektorie padá, je při zanedbání odporu vzduchu rovna době stoupání koule do tohoto bodu. V nejvyšším bodě trajektorie má koule zároveň nulovou rychlost ve vertikálním směru. Pro dráhu volného pádu platí vzorec , z nějž lze vyjádřit dobu trvání volného pádu jako 
, platí tedy:
t = √[(2 · s)/g] = √(810 m/10 m · s−2) = √(81 s−2) = 9 s.
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