Question

O macara ridica uniform la inaltimea de 12m un corp cu masa de 350kg in 20 de secunde(g~10 N/kg). Calculeaza lucrul mecanic motor si puterea mecanica a motorului macaralei.

Answer 1

$h=12 \ m \\ m=350 \ kg \\ t=20 \ s \\ g=10 \ N/kg \\ \boxed{L-?} \\ \boxed{P-?} \\ \bold{Rezolvare:} \\ \boxed{L=F_t \cdot d}=F \cdot l=G \cdot h \\ G=m \cdot g =350 \ kg \cdot 10 \ N/kg \\ G=3 \ 500 \ N \\ L=3 \ 500 \ N \cdot 12 \ m \\ \Rightarrow \boxed{L=42 \ 000 \ J=\boxed{42 \ kJ}} \\ \boxed{P=\frac{L}{t}} \\ P=\frac{42 \ 000 \ J}{20 \ s} \\ \Rightarrow \boxed{P=2 \ 100 \ W=2,1 \ kW}$