Question

Determine the correctness or otherwise of the following Assertion [p] and Reason [r].
[p]: The tenacity of a polymeric fibre depends on the strain rate
[r]: Under mechanical deformation polymeric fibre exhibits both elastic as well as viscous response

• A. Both [p] and [r] are true and [r] is the correct reason for [p]
• B. Both [p] and [r] are true but [r] is not the correct reason for [p]
• C. Both [p] and [r] are false
• D. [p] is true but [r] is false

Hint:

Polymeric fibres show both elastic and viscous behaviour under deformation, and the strain rate can influence their tenacity, with higher strain rates often increasing resistance to tensile stress.

Answer 1

The Correct Option is A

Step 1: Tenacity and Strain Rate. 
The tenacity of a polymeric fibre is the maximum tensile stress a fibre can withstand. It depends on several factors, including the strain rate. The faster the strain rate, the greater the mechanical response of the fibre, often leading to higher tenacity as it resists deformation more rapidly. Step 2: Elastic and Viscous Response. 
Polymeric materials, including fibres, exhibit both elastic and viscous behaviour under mechanical deformation. The elastic response is due to the reversible deformation, while the viscous response accounts for the energy dissipation during deformation. This dual behaviour influences the fibre's overall mechanical properties, including tenacity, at different strain rates. 
Answer: (A)