OCR MEI M1 2009 June — Question 2 7 marks

Exam BoardOCR MEI
ModuleM1 (Mechanics 1)
Year2009
SessionJune
Marks7
PaperDownload PDF ↗
Mark schemeDownload PDF ↗
TopicVectors Introduction & 2D
TypeForces in equilibrium (find unknowns)
DifficultyModerate -0.8 This is a straightforward M1 equilibrium problem requiring basic vector operations (magnitude, angle calculation) and resolving forces in two directions. The multi-part structure guides students through standard techniques with no conceptual challenges beyond applying ΣF = 0 in component form.
Spec1.10a Vectors in 2D: i,j notation and column vectors1.10d Vector operations: addition and scalar multiplication3.03m Equilibrium: sum of resolved forces = 0

2 A small box has weight \(\mathbf { W } \mathrm { N }\) and is held in equilibrium by two strings with tensions \(\mathbf { T } _ { 1 } \mathrm {~N}\) and \(\mathbf { T } _ { 2 } \mathrm {~N}\). This situation is shown in Fig. 2 which also shows the standard unit vectors \(\mathbf { i }\) and \(\mathbf { j }\) that are horizontal and vertically upwards, respectively. \begin{figure}[h]
\includegraphics[alt={},max width=\textwidth]{d6e78f93-ac2c-4053-87e4-5e5537d6dc3d-2_259_629_1795_758} \captionsetup{labelformat=empty} \caption{Fig. 2}
\end{figure} The tension \(\mathbf { T } _ { 1 }\) is \(10 \mathbf { i } + 24 \mathbf { j }\).
  1. Calculate the magnitude of \(\mathbf { T } _ { 1 }\) and the angle between \(\mathbf { T } _ { 1 }\) and the vertical. The magnitude of the weight is \(w \mathrm {~N}\).
  2. Write down the vector \(\mathbf { W }\) in terms of \(w\) and \(\mathbf { j }\). The tension \(\mathbf { T } _ { 2 }\) is \(k \mathbf { i } + 10 \mathbf { j }\), where \(k\) is a scalar.
  3. Find the values of \(k\) and of \(w\).

2 A small box has weight $\mathbf { W } \mathrm { N }$ and is held in equilibrium by two strings with tensions $\mathbf { T } _ { 1 } \mathrm {~N}$ and $\mathbf { T } _ { 2 } \mathrm {~N}$. This situation is shown in Fig. 2 which also shows the standard unit vectors $\mathbf { i }$ and $\mathbf { j }$ that are horizontal and vertically upwards, respectively.

\begin{figure}[h]
\begin{center}
  \includegraphics[alt={},max width=\textwidth]{d6e78f93-ac2c-4053-87e4-5e5537d6dc3d-2_259_629_1795_758}
\captionsetup{labelformat=empty}
\caption{Fig. 2}
\end{center}
\end{figure}

The tension $\mathbf { T } _ { 1 }$ is $10 \mathbf { i } + 24 \mathbf { j }$.\\
(i) Calculate the magnitude of $\mathbf { T } _ { 1 }$ and the angle between $\mathbf { T } _ { 1 }$ and the vertical.

The magnitude of the weight is $w \mathrm {~N}$.\\
(ii) Write down the vector $\mathbf { W }$ in terms of $w$ and $\mathbf { j }$.

The tension $\mathbf { T } _ { 2 }$ is $k \mathbf { i } + 10 \mathbf { j }$, where $k$ is a scalar.\\
(iii) Find the values of $k$ and of $w$.

\hfill \mbox{\textit{OCR MEI M1 2009 Q2 [7]}}