A timber test specimen of size 50 × 50 mm in cross-section and 150 mm in length was tested for its specific gravity. If the specimen weighs 250 g and has 15% of moisture content, calculate its specific gravity by accounting the moisture content. 

Concept:

To calculate the specific gravity of a timber specimen, we account for its dry weight and the volume of the specimen. The moisture content must be removed from the given weight to get the dry weight.

Given Data:

• Cross-sectional size = 50 mm × 50 mm
• Length = 150 mm
• Weight = 250 g
• Moisture content = 15%

Calculate the Volume of the Timber Specimen:

The volume is given by:

\( \text{Volume} = 50 \times 50 \times 150 = 375 \, \text{cm}^3 \)

Adjust the Weight for Dry Weight:

Using the formula for dry weight:

\( W_d = \frac{250}{1 + \frac{15}{100}} = \frac{250}{1.15} = 217.39 \, \text{g} \)

Calculate the Specific Gravity:

The formula for specific gravity is:

\( \text{Specific Gravity} = \frac{\text{Dry Weight}}{\text{Volume} \times \text{Density of Water}} \)

\( \text{Specific Gravity} = \frac{217.39}{375} \approx 0.579 \)

The specific gravity of the timber specimen is 0.579.