Mass

The thickness of a metallic tube is 1cm, and its outer radius is 11cm. Find the mass of such a 1m long tube if the metal density is 7.5g per cubic cm.

Correct answer:

m =  49.48 kg

Step-by-step explanation:

$$\begin{gathered} \rho =7.5{\text{g/cm}}^3 \\ l=1\text{m}\to \text{cm}=1\cdot 100\text{cm}=100\text{cm} \\ h=1\text{cm} \\ R=11\text{cm} \\ r=R-h=11-1=10\text{cm} \\ S=\pi \cdot R^2-\pi \cdot r^2=3.1416\cdot 11^2-3.1416\cdot 10^2\doteq 65.9734{\text{cm}}^2 \\ V=S\cdot l=65.9734\cdot 100\doteq 6597.3446{\text{cm}}^3 \\ {m}_1=\rho \cdot V=7.5\cdot 6597.3446\doteq 49480.0843\text{g} \\ m=m_1\to \text{kg}=m_1:1000\text{kg}=49480.0843:1000\text{kg}=49.48\text{kg}=49.48\text{kg} \end{gathered}$$

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