Solution

ID: past-exam-of-the-mathematical-methods-i-course-of-the-university-of-oxford/2017-resit/7/b/ii/solution

At critical damping, the characteristic polynomial has the repeated root . Its independent solutions are and , giving
The factor supplies the second independent solution that would be lost by using just one exponential. There is no oscillatory factor at this boundary between the underdamped and overdamped regimes.

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