| Exam Board | OCR MEI |
|---|---|
| Module | M1 (Mechanics 1) |
| Marks | 4 |
| Paper | Download PDF ↗ |
| Mark scheme | Download PDF ↗ |
| Topic | Moments |
| Type | Coplanar forces in equilibrium |
| Difficulty | Standard +0.3 This is a straightforward equilibrium problem requiring students to explain why tension is constant (smooth pulley, light string - standard bookwork) and resolve forces to find the rod force. The calculation involves basic trigonometry and force resolution with clearly given angles and masses. Slightly above average difficulty only because it combines multiple standard techniques, but requires no novel insight or complex multi-step reasoning. |
| Spec | 3.03k Connected particles: pulleys and equilibrium3.03m Equilibrium: sum of resolved forces = 03.03n Equilibrium in 2D: particle under forces |
| Answer | Marks | Guidance |
|---|---|---|
| Answer/Working | Mark | Guidance |
| String light and pulley smooth | E1 | Accept pulley smooth alone |
| \(5g\) (49) N thrust | M1 B1 A1 | Three forces in equilibrium. Allow sign errors. For \(15g\) (147) N used as tension. \(5g\) (49) N thrust. Accept \(\pm 5g\) (49). Ignore diagram. [Award SC2 for \(\pm 5g\) (49) N without 'thrust' and SC3 if it is] |
## Question 3:
| Answer/Working | Mark | Guidance |
|---|---|---|
| String light and pulley smooth | E1 | Accept pulley smooth alone |
| $5g$ (49) N thrust | M1 B1 A1 | Three forces in equilibrium. Allow sign errors. For $15g$ (147) N used as tension. $5g$ (49) N thrust. Accept $\pm 5g$ (49). Ignore diagram. [Award SC2 for $\pm 5g$ (49) N without 'thrust' and SC3 if it is] |
---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]{bf477f61-9f8f-418a-86d8-392bc30323b1-2_519_629_370_745}
\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 Q3 [4]}}