WAEC Physics 2025 Objective — Question 10
Question 10 of 51 from the West African Examinations Council (WAEC) Physics 2025 Objective paper, with the correct answer and a full explanation.
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A liquid of mass 2kg at 61°C is kept in a lagged vessel. If another 2kg of the same liquid at 21°C is added to the liquid in the vessel, calculate the final temperature of the mixture.
- A. 50°C
- B. 41°CCorrect
- C. 30°C
- D. 15°C
Explanation
Heat lost by hot liquid = heat gained by cold liquid: mc(61-T) = mc(T-21) → 60-T = T-21 → 2T = 82 → T = 41°C.
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