[tex]Dane:\\m = 60 \ kg\\E_{k} = 400 \ J\\Szukane:\\v = ?\\\\Rozwiazanie\\\\E_{k} = \frac{mv^{2}}{2} \ \ |\cdot\frac{2}{m}\\\\v^{2} =\frac{2E_{k}}{m} \ \|\sqrt{}\\\\v = \sqrt{\frac{2E_{k}}{m}}\\\\v = \sqrt{\frac{2\cdot400 \ J}{60 \ kg}}} =\sqrt{\frac{800 \ kg\cdot\frac{m^{2}}{s^{2}}}{60 \ kg}}} = \sqrt{\frac{40}{3}} \ \frac{m}{s}\\\\\boxed{v\approx3,65\frac{m}{s}}[/tex]
