Select the correct option for the given statements. Statement 1: The placing of veneers normal to each other increases the longitudinal and transverse strength of plywood. Statement 2: Plywood possesses uniform tensile strength in all directions.
- AStatement 1 is true and statement 2 is false
- BBoth statement 1 and statement 2 are false
- CStatement 1 is false and statement 2 is true
- DBoth statement 1 and statement 2 are trueCorrect
Solution
Concept
In plywood, the grain of each veneer is placed at right angles to the next, so strength is more uniform in all directions.
Step-by-step solution
1. Plywood is made of an odd number of thin veneers glued together. 2. The grain of each layer is at 90° to the next layer. 3. This cross placing gives good strength both along and across the sheet, so Statement 1 is true. 4. Standard textbooks list 'uniform tensile strength in all directions' as an advantage of plywood, so Statement 2 is taken as true. 5. Therefore both statements are true.
Explanation
Cross placing of veneers balances the weak and strong directions of the wood grain. Because of this, plywood has nearly equal strength in length and width. Textbooks state this as uniform tensile strength in all directions.
Why the other options are wrong
A, B and C are wrong because both statements are true according to standard building materials textbooks.
Shortcut
Plywood = cross grain = strength in both directions = uniform strength.
Common mistake
Marking Statement 2 false because natural wood is strong only along the grain. Plywood is different because of the cross layers.
Correct answer: D) Both statement 1 and statement 2 are true