[latex]Dane:\m = 2[kg]\T_p = 20[^oC]\t_k = 50[^oC]\P = 2000[W]\C_w = 4200 [ frac{J}{kg cdot ^oC}] \\Szukane :\t = ? \\Rozwiazanie :\P = frac{W}{t} o t = frac{W}{P} \\W = C_w cdot Delta T cdot m = C_w cdot (T_k - T_p ) cdot m \\W = 4200[ frac{J}{kg cdot ^oC} ] cdot (50[^oC] - 20[^oC] ) cdot 2 [kg] \W = 252000[J]\ = frac{252000[J]}{2000[W]} \ t = 126[s] = 2,1 [min ] [/latex]
[latex]Dane: \ \ m=2kg \ \ t_{1}=20^{o}C \ \ t_{2}=50^{o}C \ \ Delta t=t_{2}-t_{1}=50^{o}C-20^{o}C=30^{o}C \ \ P=2000W \ \ c=4200 frac{J}{kg*^{o}C} \ \ c= frac{Q}{m*Delta t} \ \ Q=m*c*Delta t \ \ Q= 2kg*4200 frac{J}{kg*^{o}C} *30^{o}C=252000J \ \ P= frac{W}{t}= frac{Q}{t} \ \ t= frac{Q}{P} \ \ t= frac{252000J}{2000W} =126[ frac{J}{ frac{J}{s} }]=126[J* frac{s}{J}]=126s [/latex]
