Question

O teava are lungimea 6 metri diametrul 80 milimetri si grosimea 6mm.Cate kg are teava stiind ca 8kg/dm cubi

Answer 1

$\bold{Formula: \ \rho= \frac{m}{V} }, \ \Rightarrow m=\rho \cdot V; \\ \rho=8 \ kg/dm^3; \\ V=\pi r^2 h \\ r= \frac{d}{2} \\ h=6 \ mm \\ d=80 \ mm \\ \Rightarrow r= \frac{80 \ mm}{2} =40 \ mm \\\Rightarrow V=\pi(40 \ mm)^2 \cdot 6 \ mm=\pi1600 \cdot 6 \ mm \\ \Rightarrow V=9600\pi \ m^3 \\ \Rightarrow m=8 \ kg/dm^3 \cdot 9600\pi \ m^3=8 \ kg/dm^3 \cdot 9 \ 600 \ 000\pi \ dm^3 \\ \Rightarrow \boxed{m=92 \ 160 \ 000 \ 000\pi \ kg}.$