OCR MEI M3 2013 January — Question 4

Exam BoardOCR MEI
ModuleM3 (Mechanics 3)
Year2013
SessionJanuary
TopicCentre of Mass 1

4
  1. The region enclosed between the curve \(y = x ^ { 4 }\) and the line \(y = h\) (where \(h\) is positive) is rotated about the \(y\)-axis to form a uniform solid of revolution. Find the \(y\)-coordinate of the centre of mass of this solid.
  2. The region \(A\) is bounded by the \(x\)-axis, the curve \(y = x + \sqrt { x }\) for \(0 \leqslant x \leqslant 4\), and the line \(x = 4\). The region \(B\) is bounded by the \(y\)-axis, the curve \(y = x + \sqrt { x }\) for \(0 \leqslant x \leqslant 4\), and the line \(y = 6\). These regions are shown in Fig. 4. \begin{figure}[h]
    \includegraphics[alt={},max width=\textwidth]{3f674569-7e99-4ba8-84f1-a1eb438e30ed-3_572_513_1779_778} \captionsetup{labelformat=empty} \caption{Fig. 4}
    \end{figure}
    1. A uniform lamina occupies the region \(A\). Show that the \(x\)-coordinate of the centre of mass of this lamina is 2.56 , and find the \(y\)-coordinate.
    2. Using your answer to part (i), or otherwise, find the coordinates of the centre of mass of a uniform lamina occupying the region \(B\).