[tex]dane:\\v = 13\frac{m}{s}\\E_{k} = 338 \ 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{676 \ J}{(13\frac{m}{s})^{2}} = \frac{676 \ kg\cdot\frac{m^{2}}{s^{2}}}{169\frac{m^{2}}{s^{2}}} = 4 \ kg\\\\Odp. \ b)[/tex]
