4.
\begin{figure}[h]
\includegraphics[alt={},max width=\textwidth]{2656d4b4-7f47-48db-9d7e-07db6ecb8606-5_496_1264_316_443}
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\caption{Figure 1}
\end{figure}
The points \(O\) and \(B\) are on horizontal ground. The point \(A\) is \(h\) metres vertically above \(O\). A particle \(P\) is projected from \(A\) with speed \(12 \mathrm {~m} \mathrm {~s} ^ { - 1 }\) at an angle \(\alpha ^ { \circ }\) to the horizontal. The particle moves freely under gravity and hits the ground at \(B\), as shown in Figure 1. The speed of \(P\) immediately before it hits the ground is \(15 \mathrm {~m} \mathrm {~s} ^ { - 1 }\).
- By considering energy, find the value of \(h\).
Given that 1.5 s after it is projected from \(A , P\) is at a point 4 m above the level of \(A\), find
- the value of \(\alpha\),
- the direction of motion of \(P\) immediately before it reaches \(B\).