5 On a fairground ride, the centre of a horizontal circular frame is attached to the top of a vertical pole, OP . When the frame and pole rotate, OP remains vertical and the frame remains horizontal.

Chairs of mass 10 kg are attached to the frame by means of chains of length 2.5 m . The chains are modelled as being both light and inextensible.

A side view of the situation when the ride is stationary is shown in Fig. 5. A chain fixed to point A on the circular frame supports a chair. The distance OA is 2 m .

\begin{figure}[h]
\begin{center}
  \includegraphics[alt={},max width=\textwidth]{37798594-8cb0-48aa-8401-090f09e25dff-5_839_1074_641_240}
\captionsetup{labelformat=empty}
\caption{Fig. 5}
\end{center}
\end{figure}

A child of mass 40 kg sits in a chair and, after a short time, the ride is rotating at a steady angular speed of $\omega$ radians per second, with the chain inclined at an angle of $50 ^ { \circ }$ to the downward vertical. The motion of the child and chair is in a horizontal circle.
\begin{enumerate}[label=(\alph*)]
\item Draw a sketch showing the forces acting on the chair when the ride is moving at this angular speed.
\item - Determine the tension in the chain.

\begin{itemize}
  \item Determine the value of $\omega$.
\end{itemize}

On another occasion, a man of mass 90 kg sits in the chair; after a short time, the ride is rotating in a horizontal circle at a steady speed of $\omega$ radians per second, with the chain inclined at the same angle of $50 ^ { \circ }$ to the downward vertical.
\item Without any detailed calculations, explain how your answers to part (b) for the child would compare with those for the man.
\item Explain why the chain is modelled as light.
\item State two other modelling assumptions that were used in answering part (b).
\end{enumerate}

\hfill \mbox{\textit{OCR MEI Further Mechanics B AS 2021 Q5 [12]}}