Consider the following statements regarding the advantages of plywood : 1. It has good strength both along as well as across the grains. 2. It will not shrink or swell across the grains. 3. It can be curved into desired shapes. Which of the above statements is/are correct ?
- A1 and 3Correct
- B1 and 2
- C2 and 3
- D2 only
Solution
Concept
Plywood has veneers glued with grains at right angles, so strength is nearly equal in both directions and movement is small, but not zero.
Step-by-step solution
1. Plywood is made of thin veneers glued so that the grain of each layer is at 90° to the next layer. 2. Statement 1: Cross layers give good strength both along and across the grain. Correct. 3. Statement 2: Cross layers reduce shrinkage and swelling a lot, but do not stop them fully. 'Will not shrink or swell' is too strong. Not correct. 4. Statement 3: Thin plywood sheets can be bent or moulded into curved shapes. Correct. 5. So statements 1 and 3 are correct. Answer is (A).
Explanation
In plywood the veneers are glued with their grains at right angles. This gives nearly equal strength in both directions and makes shrinkage and swelling very small, but not zero. Plywood sheets can also be bent into curved shapes.
Why the other options are wrong
Statement 2 claims no shrinking or swelling at all, which is not strictly true.
Shortcut
Plywood: two-way strength, less shrinkage, can be curved.
Common mistake
Accepting absolute statements.
Correct answer: A) 1 and 3