6.
\begin{figure}[h]
\includegraphics[alt={},max width=\textwidth]{c150d518-2da6-4f08-90c4-a831a31020f9-11_485_711_244_589}
\captionsetup{labelformat=empty}
\caption{Figure 4}
\end{figure}
A small ball of mass \(3 m\) is attached to the ends of two light elastic strings \(A P\) and \(B P\), each of natural length \(l\) and modulus of elasticity \(k m g\). The ends \(A\) and \(B\) of the strings are attached to fixed points on the same horizontal level, with \(A B = 2 l\). The mid-point of \(A B\) is \(C\). The ball hangs in equilibrium at a distance \(\frac { 3 } { 4 } l\) vertically below \(C\) as shown in Figure 4.
- Show that \(k = 10\)
The ball is now pulled vertically downwards until it is at a distance \(\frac { 12 } { 5 } l\) below \(C\). The ball is released from rest.
- Find the speed of the ball as it reaches \(C\).