Correct Answer: D. Rind gall
Solution:
A rind gall is a surface defect in timber characterized by a swollen area. It forms when a tree heals over a wound, such as where a branch was improperly cut off. The new layers of sapwood grow over the wound, creating a noticeable swelling or gall on the surface of the timber.
Correct Answer: A. Cleavability
Solution:
Cleavability is the property of timber that measures its resistance to splitting or the ease with which it can be split along the grain. A wood with high cleavability splits easily.
Correct Answer: A. Plies are placed at right angles with each other.
Solution:
The primary reason for plywood's dimensional stability (low expansion and shrinkage) is its cross-grained construction. By placing the veneers at right angles to each other, the tendency of one layer to swell or shrink is restricted by the adjacent layer. This balances out the internal stresses and makes the panel very stable.
Correct Answer: D. Teak
Solution:
Teak is highly valued for its exceptional durability, strength, resistance to decay and termites, and attractive appearance. These superior qualities make it one of the most sought-after and expensive timbers for high-quality furniture, boat building, and exterior construction.
Correct Answer: D. Teak
Solution:
Teak contains natural oils and silica that make it highly resistant to pests, including termites (white ants), as well as fungal decay. This natural durability is one of the key reasons it is so valued for outdoor and structural applications.
Correct Answer: C. reduces to powder
Solution:
Dry rot is a type of fungal decay that breaks down the cellulose and hemicellulose components of wood. In its advanced stages, the affected timber loses all its strength, becomes brittle, and ultimately reduces to a dry, crumbly powder.
A. It increases the weight of timber
B. It improves the strength properties of timber
Correct Answer: B. Only B
Solution:
Seasoning is the process of drying timber to remove its sap and moisture. This process reduces the weight of the timber, making statement A incorrect. By removing moisture, seasoning increases the timber's strength, stiffness, and durability, making statement B correct.
Correct Answer: D. All options are correct
Solution:
All the statements accurately describe different methods of converting logs into timber. Each method has its own advantages regarding the resulting grain pattern, strength, and susceptibility to warping.
Correct Answer: A. at right angles
Solution:
The fundamental principle of plywood construction is cross-lamination. The veneers are glued together with the grain direction of each layer oriented at right angles (90°) to the adjacent layers. This technique is what gives plywood its dimensional stability and uniform strength in all directions.
Correct Answer: C. 40 years
Solution:
While teak is exceptionally durable, for engineering and construction estimation purposes, the functional life of teak wood doors and windows is often conservatively taken as around 40 years, although they can last much longer with proper maintenance.
Correct Answer: D. Sap
Solution:
Sap is the fluid, consisting primarily of water dissolved with sugars and mineral salts, that circulates through the vascular system of a plant. It transports water and nutrients throughout the tree.
Correct Answer: A. lack of ventilation
Solution:
Dry rot is a fungal decay that thrives in moist, unventilated conditions. A lack of ventilation traps moisture and creates the perfect environment for the fungus to grow and destroy the timber.
Correct Answer: B. Annular rings
Solution:
The age of a tree can be accurately determined by counting its annular rings (or growth rings). Each ring typically represents one year of growth, showing the contrast between the light-colored wood that grows in the spring and the dark-colored wood that grows in the summer.
Correct Answer: A. Ordinary sawing
Solution:
Ordinary sawing, also known as flat sawing or through-and-through sawing, is the fastest and simplest method. It produces the maximum yield of lumber from a log with the least amount of waste, making it the most economical method.
Correct Answer: C. Both (a) and (b)
Solution:
The manufacturing process for plywood involves applying high heat and pressure to bond the veneer layers. The typical pressure range is approximately 70 to 140 N/cm². Since the ranges in both option A (100 to 150 N/cm²) and option B (100 to 130 N/cm²) largely fall within or overlap with the standard accepted pressure range, both are considered correct in this context.