AQA M2 — Question 1

Exam BoardAQA
ModuleM2 (Mechanics 2)
PaperDownload PDF ↗
Mark schemeDownload PDF ↗
TopicMoments
TypeBeam suspended by vertical ropes
DifficultyModerate -0.3 This is a straightforward two-rope equilibrium problem requiring resolution of vertical forces and taking moments about one point. The uniform beam setup is standard, and the calculation involves basic arithmetic with clearly given values. Slightly easier than average due to its routine nature, though it requires understanding of moments and equilibrium conditions.
Spec3.04a Calculate moments: about a point3.04b Equilibrium: zero resultant moment and force

1 A uniform beam, \(A B\), has mass 20 kg and length 7 metres. A rope is attached to the beam at \(A\). A second rope is attached to the beam at the point \(C\), which is 2 metres from \(B\). Both of the ropes are vertical. The beam is in equilibrium in a horizontal position, as shown in the diagram. \includegraphics[max width=\textwidth, alt={}, center]{88aec6ab-af83-4d5e-84b6-5fd84c16a6c9-003_298_906_756_552} Find the tensions in the two ropes.

Question 1:
Part (a)(i)
AnswerMarks Guidance
\(\mathbf{a} = \frac{d\mathbf{v}}{dt} = -8\sin 2t\,\mathbf{i} + 3\cos t\,\mathbf{j}\)M1 Differentiate velocity
\(\mathbf{F} = 4\mathbf{a} = (-32\sin 2t\,\mathbf{i} + 12\cos t\,\mathbf{j})\) NA1A1 A1 each component
Part (a)(ii)
AnswerMarks Guidance
At \(t = \pi\): \(\mathbf{F} = (-32\sin 2\pi\,\mathbf{i} + 12\cos\pi\,\mathbf{j}) = (0\,\mathbf{i} - 12\,\mathbf{j})\)M1 Substitute \(t=\pi\)
\(\mathbf{F} = 12\) N
Part (b)
AnswerMarks Guidance
\(\mathbf{r} = \int \mathbf{v}\,dt = 2\sin 2t\,\mathbf{i} - 3\cos t\,\mathbf{j} + \mathbf{c}\)M1 Integrate velocity
At \(t=0\): \(2\mathbf{i} - 14\mathbf{j} = 0\,\mathbf{i} - 3\mathbf{j} + \mathbf{c}\), so \(\mathbf{c} = 2\mathbf{i} - 11\mathbf{j}\)M1 Apply initial condition
\(\mathbf{r} = (2\sin 2t + 2)\,\mathbf{i} + (-3\cos t - 11)\,\mathbf{j}\)A1A1A1 A1 each component correct, A1 constant
# Question 1:

## Part (a)(i)
| $\mathbf{a} = \frac{d\mathbf{v}}{dt} = -8\sin 2t\,\mathbf{i} + 3\cos t\,\mathbf{j}$ | M1 | Differentiate velocity |
|---|---|---|
| $\mathbf{F} = 4\mathbf{a} = (-32\sin 2t\,\mathbf{i} + 12\cos t\,\mathbf{j})$ N | A1A1 | A1 each component |

## Part (a)(ii)
| At $t = \pi$: $\mathbf{F} = (-32\sin 2\pi\,\mathbf{i} + 12\cos\pi\,\mathbf{j}) = (0\,\mathbf{i} - 12\,\mathbf{j})$ | M1 | Substitute $t=\pi$ |
|---|---|---|
| $|\mathbf{F}| = 12$ N | A1 | |

## Part (b)
| $\mathbf{r} = \int \mathbf{v}\,dt = 2\sin 2t\,\mathbf{i} - 3\cos t\,\mathbf{j} + \mathbf{c}$ | M1 | Integrate velocity |
|---|---|---|
| At $t=0$: $2\mathbf{i} - 14\mathbf{j} = 0\,\mathbf{i} - 3\mathbf{j} + \mathbf{c}$, so $\mathbf{c} = 2\mathbf{i} - 11\mathbf{j}$ | M1 | Apply initial condition |
| $\mathbf{r} = (2\sin 2t + 2)\,\mathbf{i} + (-3\cos t - 11)\,\mathbf{j}$ | A1A1A1 | A1 each component correct, A1 constant |

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1 A uniform beam, $A B$, has mass 20 kg and length 7 metres. A rope is attached to the beam at $A$. A second rope is attached to the beam at the point $C$, which is 2 metres from $B$. Both of the ropes are vertical. The beam is in equilibrium in a horizontal position, as shown in the diagram.\\
\includegraphics[max width=\textwidth, alt={}, center]{88aec6ab-af83-4d5e-84b6-5fd84c16a6c9-003_298_906_756_552}

Find the tensions in the two ropes.

\hfill \mbox{\textit{AQA M2  Q1}}