Oak trunk

Calculate in tonnes the approximate weight of a cylindrical oak trunk with a diameter of 66 cm and a length of 4 m, knowing that the density of the wood was 800 kg/m³.

Correct answer:

m =  1.0948 t

Step-by-step explanation:

$$\begin{gathered} D=66\text{cm}\to \text{m}=66:100\text{m}=0.66\text{m} \\ l=4\text{m} \\ \rho =800{\text{kg/m}}^3 \\ r=D/2=0.66/2=\frac{33}{100}=0.33\text{m} \\ S=\pi \cdot r^2=3.1416\cdot 0.33^2\doteq 0.3421{\text{m}}^2 \\ V=S\cdot l=0.3421\cdot 4\doteq 1.3685{\text{m}}^3 \\ {m}_1=V\cdot \rho =1.3685\cdot 800\doteq 1094.7822\text{kg} \\ m=m_1\to \text{t}=m_1:1000\text{t}=1094.7822:1000\text{t}=1.095\text{t}=1.0948\text{t} \end{gathered}$$

Try another example