[tex]dane:\\m = 5 \ kg\\W = 810 \ J\\szukane:\\v = ?\\\\W = E_{k} = \frac{mv^{2}}{2}\\\\W = \frac{mv^{2}}{2} \ \ /\cdot\frac{2}{m}\\\\v^{2} = \frac{2W}{m}\\\\v = \sqrt{\frac{2W}{m}}\\\\v = \sqrt{\frac{2\cdot810 \ J}{5 \ kg}} = \sqrt{\frac{1620 \ kg\cdot\frac{m^{2}}{s^{2}}}{5 \ kg}} = \sqrt{324\frac{m^{2}}{s^{2}}}\\\\v = 18\frac{m}{s}[/tex]
