[tex]dane:\\P = 2,4 \ kW = 2,4\cdot1000 \ W = 2 \ 400 \ W\\W = 0,9 \ MJ = 0,9\cdot1 \ 000 \ 000 \ J = 900 \ 000 \ J\\szukane:\\t = ?\\\\Rozwiazanie\\\\P = \frac{W}{t} \ \ /\cdot t\\\\P\cdot t = W \ \ /:P\\\\t = \frac{W}{P}\\\\t = \frac{900 \ 000 \ J}{2 \ 400 \ W} = \frac{900 \ 000 \ kg\cdot\frac{m^{2}}{s^{2}}}{2 \ 400 \ kg\cdot\frac{m}{s^{2}}} = 375 \ s = 6 \ min \ i \ 15 \ s[/tex]
