[tex]dane:\\V = 20 \ cm^{3}=0,00002 \ m^{3}\\d = 7800\frac{kg}{m^{3}} \ - \ gestosc \ stali\\g = 10\frac{N}{kg} \ - \ przyspieszenie \ ziemskie\\szukane:\\F_{g} = ?\\\\\underline{F_{g} = m\cdot g}\\\\ale:\\\\d = \frac{m}{V} \ \ \rightarrow \ \ m = d\cdot V\\\\m = 7800\frac{kg}{m^{3}}\cdot0,00002 \ m^{3} = 0,156 \ kg\\\\F_{g} = 0,156 \ kg\cdot10\frac{N}{kg}\\\\\boxed{F_{g} = 1,56 \ N}[/tex]
Odp. Ciężar tej kulki Fg = 1,56 N.
