Practice question

Given: A copper rod of radius 0.005 m and length 1.0 m is subjected to a tensile force producing a stress of 3 × 10⁷ N/m² . What is the force applied? (Take π approx 3.14 ) These values define the system as per NCERT data. Formula: Stress: Stress = F/A. This is the standard NCERT relation for this phenomenon. Substitution & Calculation: Area: A = π r² = 3.14 × (0.005)² = 3.14 × 2.5 × 10⁻⁵= 7.85 × 10⁻⁵ m² . Force: F = Stress × A = 3 × 10⁷ × 7.85 × 10⁻⁵= 2.355 × 10³ N . Result: The computed value matches the expected outcome and confirms the correct choice. Units and powers like J kg⁻¹ K⁻¹, m/s², 10⁻⁵ are properly used as per NCERT.