Question

O macara cu puterea 8.82 kW a ridicat un corp cu masa 4.5 t la o inaltime de 8 m. In cat timp a facut aceasta lucrare? Se da g=9.8 N/kg
URGENTTTT!!!

Answer 1

P=8,82 kW--->P= 8820 W
m=4,5 t--->m=4500 kg
h=8 m
g=9,8 N/kg
t=?
Aflam Greutatea:
G=m*g
G= 4500kg*9,8N/kg= 44.100 N
Observam ca Forta=Greutatea
F= 44.100N
Aflam lucrul mecanic:F=G; d=h;
L=G*h 
L=44.100N*8m = 352.800 J
$P= \frac{L}{t} =\ \textgreater \ t= \frac{L}{P}$
t=$\frac{352.800J}{8820W} =40 secunde$
t= 40 s