| Exam Board | OCR MEI |
|---|---|
| Module | M1 (Mechanics 1) |
| Year | 2007 |
| Session | June |
| Marks | 4 |
| Paper | Download PDF ↗ |
| Mark scheme | Download PDF ↗ |
| Topic | Moments |
| Type | Modelling assumptions justification |
| Difficulty | Moderate -0.8 This is a straightforward equilibrium problem requiring students to recall a standard modelling assumption (smooth pulley means constant tension) and resolve forces vertically. The calculation involves simple arithmetic with given weights, and the conceptual demand is minimal—well below average A-level difficulty. |
| Spec | 3.03k Connected particles: pulleys and equilibrium |
| Answer | Marks | Guidance |
|---|---|---|
| Answer | Marks | Guidance |
| The string is light and the pulley is smooth | B1 | Must mention both light string and smooth pulley |
| Answer | Marks | Guidance |
|---|---|---|
| Answer | Marks | Guidance |
| Tension in string \(= 15g = 147\) N | B1 | |
| Resolving vertically for P: Rod force \(+ 147 = 20g + 147\) | M1 | Correct equation for vertical equilibrium |
| Rod force \(= 20g = 196\) N, thrust | A1 | Must state thrust |
# Question 3:
## Part (i)
| Answer | Marks | Guidance |
|--------|-------|----------|
| The string is light and the pulley is smooth | B1 | Must mention both light string and smooth pulley |
## Part (ii)
| Answer | Marks | Guidance |
|--------|-------|----------|
| Tension in string $= 15g = 147$ N | B1 | |
| Resolving vertically for P: Rod force $+ 147 = 20g + 147$ | M1 | Correct equation for vertical equilibrium |
| Rod force $= 20g = 196$ N, thrust | A1 | Must state thrust |
---3 Fig. 3 shows a system in equilibrium. The rod is firmly attached to the floor and also to an object, P. The light string is attached to P and passes over a smooth pulley with an object Q hanging freely from its other end.
\begin{figure}[h]
\begin{center}
\includegraphics[alt={},max width=\textwidth]{3be85526-3872-42ac-8278-1d4a3cf75ff7-3_526_633_429_708}
\captionsetup{labelformat=empty}
\caption{Fig. 3}
\end{center}
\end{figure}
(i) Why is the tension the same throughout the string?\\
(ii) Calculate the force in the rod, stating whether it is a tension or a thrust.
\hfill \mbox{\textit{OCR MEI M1 2007 Q3 [4]}}