Salut,
Notăm cu l - lungimea ţevii, cu d_ext - diametrul exterior, d_int - diametrul interior, d_ext = 0,08 m = 8·10⁻² m, d_int = 0,06 m = 6·10⁻² m.
Masa ţevii este m = V * ρ, unde V este volumul ţevii, iar ρ este densitatea materialului ţevii.
[tex]\rho=11,3\ g/cm^3=11,3\dfrac{10^{-3}}{10^{-6}}\ kg/m^3=11300\ kg/m^3;\\\\V=V_{exterior}-V_{interior}=l\cdot\dfrac{\pi\cdot d^{\tiny{2}}_{ext}}{4}-l\cdot\dfrac{\pi\cdot d^{\tiny{2}}_{int}}{4}=\\\\=\dfrac{l\cdot\pi}4\cdot(d^{\tiny{2}}_{ext}-d^{\tiny{2}}_{int})=\dfrac{2,5\cdot\pi}4\left[(8\cdot10^{-2})^2-(6\cdot10^{-2})^2\right]=\\\\=\dfrac{2,5\cdot\pi}4\left(64\cdot10^{-4}-36\cdot10^{-4}\right)=17,5\pi\cdot10^{-4}\ m^3;\\\\m=11300\ kg/m^3\cdot17,5\pi\cdot 10^{-4}\ m^3=62,12\ kg.[/tex]
Green eyes.
