JEE Mathematics · Hard

Differential Equations: Mixed MCQ

Solve this quality-checked JEE multiple-choice question, then review the correct answer and explanation.

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MixedHardQuestion 370012

Question

Newton's law of cooling: dT/dt = −k(T−T₀). After solving, T(t) is:
  1. A
    T₀ + (T_initial − T₀)e^(−kt)
    Correct
  2. B
    T₀ × e^(−kt)
  3. C
    T_initial × e^(−kt)
  4. D
    T₀ + T_initial e^(kt)

Correct answer

T₀ + (T_initial − T₀)e^(−kt)

Explanation

dT/dt = −k(T−T₀). Let u = T−T₀: du/dt = −ku → u = Ae^(−kt) → T−T₀ = (T_i−T₀)e^(−kt) → T = T₀ + (T_i−T₀)e^(−kt). As t→∞, T→T₀.