[tex]Dane:\\v = 10\frac{m}{s}\\E_{k} = \frac{5}{10} \ kJ = 0,5 \ kJ = 0,5\cdot1000 \ J = 500 \ J\\Szukane:\\m = ?\\\\Rozwiazanie\\\\E_{k} = \frac{mv^{2}}{2} \ \ \ |\cdot 2\\\\mv^{2}=2E_{k} \ \ \ /:v^{2}\\\\m = \frac{2E_{k}}{v^{2}}\\\\m = \frac{2\cdot500 \ J}{(10\frac{m}{s})^{2}} = \frac{1000 \ kg\cdot\frac{m^{2}}{s^{2}}}{100\frac{m^{2}}{s^{2}}}\\\\\boxed{m = 10 \ kg}[/tex]
Odp. Masa tego ciała m = 10 kg.
