[tex]Dane:\\m = 400 \ kg\\v = 6\frac{m}{s}\\h = 30 \ m\\g = 10\frac{N}{kg}\\Szukane:\\E_{m} = ?\\\\Rozwiazanie\\\\E_{m} = E_{p}+E_{k}\\\\E_{p} = mgh = 400 \ kg\cdot10\frac{N}{kg}\cdot30 \ m = 120 \ 000 \ J\\\\E_{k} = \frac{1}{2}mv^{2} = \frac{1}{2}\cdot400 \ kg\cdot(6\frac{m}{s})^{2} = 7 \ 200 \ J\\\\E_{m} = 120 \ 000 \ J + 7 \ 200 \ J\\\\\boxed{E_{m} = 127 \ 200 \ J = 127,2 \ kJ}\\\\(1 \ kJ = 1000 \ J)[/tex]