A 0.2kg tungsten block at 250∘C is dropped into 0.5kg water at 18∘C in a 0.1kg silver calorimeter at 18∘C. What is the f
0.2×134×(250−T) = (0.5×4186+0.1×236)×(T−18). 6700−26.8T = (2093+23.6)×(T−18) = 2116.6T−38098.8. 6700+38098.8 = 2116.6T+26.8T. 44798.8 = 2143.4T⇒T≈20.9∘C. As per NCERT, applying relevant law/formula with correct units and sign convention leads to 20.9°C. This satisfies dimensional consistency and physical conditions given, so option A is scientifically correct.
Ref: NCERT Class 11 Physics, Chapter 11: Thermal Properties – Calorimetry.