[tex]dane:\\P = 300 \ kW = 300\cdot1000 \ W = 300 \ 000 \ W\\t = 0,5 \ min = 0,5\cdot60 \ s = 30 \ s\\szukane:\\W = ?\\\\P = \frac{W}{t} \ \ /\cdot t\\\\W = P\cdot t\\\\W = 300000 \ W\cdot30 \ s\\\\W = 9 \ 000 \ 000 \J = 9 \ 000 \ kJ = 9 \ MJ\\\\\\1 \ kJ = 1000 \ J\\1 \ MJ = 1 \ 000 \ 000 \ J[/tex]