SPS SPS FM Mechanics 2025 January — Question 5

Exam BoardSPS
ModuleSPS FM Mechanics (SPS FM Mechanics)
Year2025
SessionJanuary
TopicCentre of Mass 2

5. \begin{figure}[h]
\includegraphics[alt={},max width=\textwidth]{7ecb33af-c165-4b72-98f2-7574fad3fdd5-10_881_1301_173_397} \captionsetup{labelformat=empty} \caption{Figure 3}
\end{figure} A uniform solid right circular cylinder has height \(h\) and radius \(r\). The centre of one plane face is \(O\) and the centre of the other plane face is \(Y\). A cylindrical hole is made by removing a solid cylinder of radius \(\frac { 1 } { 4 } r\) and height \(\frac { 1 } { 4 } h\) from the end with centre \(O\). The axis of the cylinder removed is parallel to \(O Y\) and meets the end with centre \(O\) at \(X\), where \(O X = \frac { 1 } { 4 } r\). One plane face of the cylinder removed coincides with the plane face through \(O\) of the original cylinder. The resulting solid \(S\) is shown in Figure 3.
  1. Show that the centre of mass of \(S\) is at a distance \(\frac { 85 h } { 168 }\) from the plane face
    containing \(O\). containing \(O\). The solid \(S\) is freely suspended from \(O\). In equilibrium the line \(O Y\) is inclined at an angle \(\arctan ( 17 )\) to the horizontal.
  2. Find \(r\) in terms of \(h\).
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