| Exam Board | AQA |
|---|---|
| Module | Paper 2 (Paper 2) |
| Year | 2020 |
| Session | June |
| Marks | 3 |
| Paper | Download PDF ↗ |
| Mark scheme | Download PDF ↗ |
| Topic | Moments |
| Type | Uniform beam on two supports |
| Difficulty | Moderate -0.8 This is a straightforward moments equilibrium problem requiring only one equation (taking moments about C) and basic knowledge that a uniform rod's weight acts at its center. The calculation is simple arithmetic with no conceptual challengesโsignificantly easier than average A-level questions which typically require multiple techniques or problem-solving insight. |
| Spec | 3.04a Calculate moments: about a point3.04b Equilibrium: zero resultant moment and force |
| Answer | Marks |
|---|---|
| 13(a) | Finds a moment of a force about |
| Answer | Marks | Guidance |
|---|---|---|
| instead of g | 3.4 | M1 |
| Answer | Marks | Guidance |
|---|---|---|
| CAO | 1.1b | A1 |
| = 3๐จ๐จ Subtotal | 2 |
| Answer | Marks |
|---|---|
| 13(b) | Explains that the weight of the rod |
| Answer | Marks | Guidance |
|---|---|---|
| (of the rod) OE | 3.5a | E1 |
| Answer | Marks | Guidance |
|---|---|---|
| Subtotal | 1 | |
| Question Total | 3 | |
| Q | Marking Instructions | AO |
Question 13:
--- 13(a) ---
13(a) | Finds a moment of a force about
any point.
Must have the form force x
distance.
Can be awarded for example for
2w, 7w, 5R, 2R
Condone use of 9.8, 9.81, 10
instead of g | 3.4 | M1 | 2๐๐ = 1.5ร 4๐จ๐จ
๐๐ = 3๐จ๐จ
Obtains w
CAO | 1.1b | A1
= 3๐จ๐จ Subtotal | 2
--- 13(b) ---
13(b) | Explains that the weight of the rod
acts through the midpoint or the
centre of mass is at the midpoint
(of the rod) OE | 3.5a | E1 | The rod is uniform so its weight
acts at the centre
Subtotal | 1
Question Total | 3
Q | Marking Instructions | AO | Marks | Typical SolutionA uniform rod, $AB$, has length $7$ metres and mass $4$ kilograms.
The rod rests on a single fixed pivot point, $C$, where $AC = 2$ metres.
A particle of weight $W$ newtons is fixed at $A$, as shown in the diagram.
\includegraphics{figure_13}
The system is in equilibrium with the rod resting horizontally.
\begin{enumerate}[label=(\alph*)]
\item Find $W$, giving your answer in terms of $g$.
[2 marks]
\item Explain how you have used the fact that the rod is uniform in part (a).
[1 mark]
\end{enumerate}
\hfill \mbox{\textit{AQA Paper 2 2020 Q13 [3]}}