Match the following lists :
| List-I (Defects in timber) | List-II |
|---|---|
| P.Cupping | 1.Caused by wood limbs encased by wood of the free trunk |
| Q.Bowing | 2.Caused by grain irregularities in the board |
| R.Checks | 3.Small cracks appearing at the ends of boards due to rapid drying |
| S.Knots | 4.Unequal shrinking in the radial and tangential direction |
Select the correct answer using the code given below :
- A2 4 1 3
- B4 2 3 1Correct
- C1 2 4 3
- D3 1 2 4
Solution
Concept
Seasoning defects and natural defects of timber
Step-by-step solution
1. Cupping: curving across the width, due to unequal shrinkage in radial and tangential directions → 4. 2. Bowing: curvature along the length, linked to grain irregularities → 2. 3. Checks: small cracks at the ends due to rapid drying → 3. 4. Knots: formed where wood limbs are encased by the trunk wood → 1. So P-4, Q-2, R-3, S-1.
Explanation
Cupping arises because timber shrinks more in the tangential direction than in the radial direction. Knots are the bases of branches enclosed in the trunk. Checks are cracks from rapid drying at the ends.
Why the other options are wrong
The other codes pair knots or checks with the wrong description, for example linking checks (drying cracks) with knots (branch bases).
Shortcut
Knot = branch; check = fast drying crack; cup = tangential vs radial shrinkage.
Common mistake
Mixing cupping and bowing.
Correct answer: B) 4 2 3 1