[tex]E_c=300 \ kJ=300 \ 000 \ J \\ v=72 \ km/h=20 \ m/s \\ \boxed{m-?} \\ \bold{Rezolvare:} \\ \boxed{E_c=\frac{m \cdot v^2}{2}}\\ m \cdot v^2=E_c \cdot 2 \\ m=\frac{2E_c}{v^2} \\ m=\frac{300 \ 000 \ J \cdot 2}{(20 \ m/s)^2} \\ m=\frac{600 \ 000 \ J}{400 \ m^2/s^2} \\ \Rightarrow \boxed{m=1 \ 500 \ kg=\bold{1,5 \ t}} [/tex]
