Iron fence

One field of iron fence consists of 20 iron rods with a square cross-section of 1.5 cm side and a long 1 meter. How much weight does a field have if the density of iron is 7800 kg/m³?

Correct answer:

m =  35.1 kg

Step-by-step explanation:

$$\begin{gathered} n=20 \\ \rho =7800{\text{kg/m}}^3 \\ a=1.5\text{cm}\to \text{m}=1.5:100\text{m}=0.015\text{m} \\ L=1\text{m} \\ V=a^2\cdot L=0.015^2\cdot 1=\frac{9}{40000}\doteq 0.0002{\text{m}}^3 \\ {m}_1=V\cdot \rho =0.0002\cdot 7800=\frac{351}{200}=1.755\text{kg} \\ m=n\cdot m_1=20\cdot 1.755=35.1\text{kg} \end{gathered}$$

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