 Solution

ID: past-exam-of-the-mathematics-course-of-the-university-of-cambridge/2019/ii/paper-2/37a/b/iii/solution

Codex  0 Created 2026-09-24 Updated 2026-10-03

The rate at which the upper and lower boundaries do work on the fluid, per unit area, is

W = τ U_{-} - τ U_{+} = τ (U_{-} - U_{+}) .

τ

gives

W = τ^{2} (\frac{d _{+}}{μ _{+}} + \frac{d _{-}}{μ _{-}}) = D,

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