Question

Ce masa are o sarma de fier lunga de 200m si cu diametrul de 4 mm ( p= 7800kg\m³)
Va rog ajutati-ma , dau coroana

Answer 1

$l=200 \ m \\ d=4 \ mm =0,004 \ m \\ \rho=7 \ 800 \ kg/m^3 \\ \rho=\frac{m}{V}; \ \ \Rightarrow m=\rho \cdot V \\ V=\pi R^2l \\ d=2R; \ \ \Rightarrow R=\frac{d}{2}=\frac{0,004 \ m}{2}=0,002 \ m \\ V=\pi (0,002 \ m)^2 \cdot 200 \ m=3,14 \cdot 200 \ m \cdot 0,000 \ 004 \ m^2=0,002 \ 5 \ m^3 \\ m=7 \ 800 \ kg/m^3 \cdot 0,002 \ 5 \ m^3=19,59 \ kg \\ \Rightarrow \boxed{\bold{m=19,6 \ kg}}$