10.
\begin{figure}[h]
\includegraphics[alt={},max width=\textwidth]{e678bf51-6dca-4ad7-808b-dfa31b04dc63-22_719_1333_246_365}
\captionsetup{labelformat=empty}
\caption{Figure 2}
\end{figure}
A boy throws a stone with speed \(U \mathrm {~ms} ^ { - 1 }\) from a point \(O\) at the top of a vertical cliff. The point \(O\) is 18 m above sea level.
The stone is thrown at an angle \(\alpha\) above the horizontal, where \(\tan \alpha = \frac { 3 } { 4 }\).
The stone hits the sea at the point \(S\) which is at a horizontal distance of 36 m from the foot of the cliff, as shown in Figure 2.
The stone is modelled as a particle moving freely under gravity with \(g = 10 \mathrm {~m} \mathrm {~s} ^ { - 2 }\)
Find
- the value of \(U\),
- the speed of the stone when it is 10.8 m above sea level, giving your answer to 2 significant figures.
- Suggest two improvements that could be made to the model.