| Exam Board | Edexcel |
|---|---|
| Module | M1 (Mechanics 1) |
| Marks | 7 |
| Paper | Download PDF ↗ |
| Mark scheme | Download PDF ↗ |
| Topic | Moments |
| Type | Non-uniform beam on supports |
| Difficulty | Standard +0.3 This is a standard M1 moments question requiring two equilibrium equations (moments about A, then vertical forces). The setup is straightforward with clearly given distances, and students follow a routine procedure: take moments to find weight, then resolve vertically for reaction. Slightly above average difficulty only because it requires careful organization of the moment equation with multiple distances. |
| Spec | 3.04b Equilibrium: zero resultant moment and force3.04c Use moments: beams, ladders, static problems |
| Answer | Marks | Guidance |
|---|---|---|
| (a) \(M(A): 1.4W = 3.15 \times 12\) where \(W = 27\) N | M1 A1 M1 A1 | |
| (b) \(R + 12 = 27\) where \(R = 15\) N | M1 A1 | |
| (c) Bar stays rigid (in a straight line); weight not acting at centre | B1 | Total: 7 marks |
**(a)** $M(A): 1.4W = 3.15 \times 12$ where $W = 27$ N | M1 A1 M1 A1 |
**(b)** $R + 12 = 27$ where $R = 15$ N | M1 A1 |
**(c)** Bar stays rigid (in a straight line); weight not acting at centre | B1 | **Total: 7 marks**An iron bar $AB$, of length $4$ m, is kept in a horizontal position by a support at $A$ and a wire attached to the point $P$ on the bar, where $PB = 0.85$ m. The bar is modelled as a non-uniform rod whose centre of mass is at $G$, where $AG = 1.4$ m, and the wire is modelled as a light inextensible string. Given that the tension in the wire is $12$ N, calculate
\begin{enumerate}[label=(\alph*)]
\item the weight of the bar, \hfill [4 marks]
\item the magnitude of the reaction on the bar at $A$. \hfill [2 marks]
\item State briefly how you have used the given modelling assumption about the bar. \hfill [1 mark]
\end{enumerate}
\hfill \mbox{\textit{Edexcel M1 Q2 [7]}}