WAEC Physics 2014 Objective — Question 22
Question 22 of 50 from the West African Examinations Council (WAEC) Physics 2014 Objective paper, with the correct answer and a full explanation.
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A quantity of water at 20°C is mixed with an equal/given quantity of hot water at 70°C. The final steady temperature of the mixture is 40°C. Determine the ratio of the mass of the cold water to that of the hot water.
- A. 7:2
- B. 3:2Correct
- C. 2:5
- D. 1:2
Explanation
Heat gained by cold water = heat lost by hot water: m_cold×(40−20) = m_hot×(70−40), so m_cold×20 = m_hot×30, giving a ratio of 3:2.
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