Practice question

Given: A stone falls freely from a height of 19.6 m . How long does it take to reach the ground? (Take g = 9.8 m/s² ) These values define the system as per NCERT data. Formula: For free fall, use y = 1/2 g t². This is the standard NCERT relation for this phenomenon. Substitution & Calculation: Here, y = 19.6 m, g = 9.8 m/s² . Substitute: 19.6 = 1/2 · 9.8 · t² Rightarrow 19.6 = 4.9 t² Rightarrow t² = 4 Rightarrow t = 2 s . The time taken is 2 s . 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.