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For Newton's law of cooling, body at 80°C cools in room at 20°C. After time, T = 60°C. Find k if time = 5 min:

Ak = ln 60
Bk = 1
Ck = (1/5) ln(3/2) ≈ 0.081 min⁻¹
Dk = 0
Answer & Solution
Correct answer: C. k = (1/5) ln(3/2) ≈ 0.081 min⁻¹
T - T_env = (T₀ - T_env) e^(-kt). 60 - 20 = 60 e^(-5k) We have → 40 = 60 e^(-5k) → e^(-5k). So → 40 = 2/3. We have → -5k = ln(2/3) → k. So → -5k = (1/5) ln(3/2) ≈ 0.081.
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