1 An object C is moving along a vertical straight line. Fig. 1 shows the velocity-time graph for part of its motion. Initially C is moving upwards at $14 \mathrm {~m} \mathrm {~s} ^ { - 1 }$ and after 10 s it is moving downwards at $6 \mathrm {~m} \mathrm {~s} ^ { - 1 }$.

\begin{figure}[h]
\begin{center}
  \includegraphics[alt={},max width=\textwidth]{e36ef805-beff-4125-b332-439ccb0d91c4-2_878_933_479_607}
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\caption{Fig. 1}
\end{center}
\end{figure}

C then moves as follows.

\begin{itemize}
  \item In the interval $10 \leqslant t \leqslant 15$, the velocity of C is constant at $6 \mathrm {~m} \mathrm {~s} ^ { - 1 }$ downwards.
  \item In the interval $15 \leqslant t \leqslant 20$, the velocity of C increases uniformly so that C has zero velocity at $t = 20$.\\
(i) Complete the velocity-time graph for the motion of C in the time interval $0 \leqslant t \leqslant 20$.\\
(ii) Calculate the acceleration of C in the time interval $0 < t < 10$.\\
(iii) Calculate the displacement of C from $t = 0$ to $t = 20$.
\end{itemize}

\hfill \mbox{\textit{OCR MEI M1 2011 Q1 [8]}}