Modelová Otázka ID 3216 - 
Těleso o objemu 50 ml a hmotnosti 200 g v nádobě vyplněné 2 litry vody (ρ = 1 000 kg/m3) klesá ke dnu rychlostí 10 cm/s. Jak velká síla působí na těleso proti směru jeho pohybu?
Správná odpověď je: B
Na těleso v kapalině a v tíhovém poli za všech okolností musí působit tíhová síla 
a vztlaková síla 
, kde ρ je hustota kapaliny vytlačovaná tělesem. Proti pohybu tělesa směrem dolů působí vztlaková síla, platí tak:
Fvz = 0,00005 m3 · 1 000 kg · m−3 · 10 m · s−2 = 0,05 kg. 10 m · s−2 = 0,5 N.
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