[tex]Dane:\\m = 2 \ 000 \ kg\\v_1 = 10\frac{m}{s}\\v_2 = 20\frac{m}{s}\\Szukane:\\W = ?\\\\\\W = E_{k_2}-E_{k_1}\\\\E_{k} = \frac{1}{2}mv^{2}\\\\W = \frac{1}{2}mv_2^{2}-\frac{1}{2}mv_1^{2}\\\\W = \frac{1}{2}m(v_2^{2}-v_1^{2})\\\\W = \frac{1}{2}\cdot2000 \ kg\cdot[(20\frac{m}{s})^{2}-(10\frac{m}{s})^{2})]\\\\W = 1000 \ kg\cdot(400-100)\frac{m^{2}}{s^{2}}\\\\W = 1000 \ kg\cdot300\frac{m^{2}}{s^{2}}\\\\\boxed{W = 300 \ 000 \ J = 300 \ kJ}\\\\(1 \ kJ = 1000 \ J)[/tex]
