For $C=0$, the increasing branch with $W(0)=0$ satisfies $W'=\sqrt{2W}$, hence
$$
\boxed{W(Z)=\frac12Z^2,
\qquad A(Z)\propto\frac2{Z^2}.}
$$
The thread thins algebraically, and the tensile vertical stress is proportional to $W'=Z$.


Solution

Past exam of the mathematics course of the University of Cambridge / 2025 / iii / Paper 329 / 2 / a / i / Solution

 Solution

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