6. The diagram shows a slide, \(A B C\), at a water park. The shape of the slide may be modelled by two circular arcs, \(A B\) and \(B C\), in the same vertical plane. Arc \(A B\) has radius 7 m and subtends an angle \(\alpha\) at its centre \(D\), where \(\cos \alpha = \frac { 9 } { 10 }\). Arc \(B C\) has radius 5 m and subtends an angle of \(45 ^ { \circ }\) at its centre, \(O\). The straight line \(D B O\) is vertical.
\includegraphics[max width=\textwidth, alt={}, center]{b6b77d92-acb6-4cc3-8328-1899ed4a87cd-7_1171_940_630_552}
Users of the slide are required to sit in a rubber ring and are released from rest at point \(A\). A girl decides to use the slide. The combined mass of the girl and the rubber ring is 50 kg .
- When the rubber ring is at a point \(P\) on the circular arc \(B C\), its speed is \(v \mathrm {~ms} ^ { - 1 }\) and \(O P\) makes an angle \(\theta\) with the upward vertical.
- Show that \(v ^ { 2 } = 111.72 - 98 \cos \theta\).
- Find, in terms of \(\theta\), the reaction between the rubber ring and the slide at \(P\).
- Show that, according to this model, the rubber ring loses contact with the slide before reaching \(C\).
- In reality, there will be resistive forces opposing the motion of the rubber ring. Explain how this fact will affect your answer to (iii).
- Show that the rubber ring will remain in contact with the slide along the arc \(A B\).