Practice question

Given: A 0.3 g drop falls from 500 m and hits the ground at 15 m/s . What is the work done by air resistance? (Take g = 10 m/s² ) These values define the system as per NCERT data. Formula: Work by gravity W_g = mgh = 0.0003 × 10 × 500 = 1.5 J. This is the standard NCERT relation for this phenomenon. Substitution & Calculation: Final K = 1/2 × 0.0003 × 15² = 0.03375 J . K_f = W_g + W_r Rightarrow 0.03375 = 1.5 + W_r Rightarrow W_r = -1.46625 J approx -1.47 J . 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.