| Exam Board | OCR |
|---|---|
| Module | M1 (Mechanics 1) |
| Year | 2015 |
| Session | June |
| Marks | 15 |
| Paper | Download PDF ↗ |
| Mark scheme | Download PDF ↗ |
| Topic | Pulley systems |
| Type | Multi-stage motion: changing surface conditions or external intervention |
| Difficulty | Standard +0.3 This is a standard M1 pulley problem with connected particles on an inclined plane. While it has multiple parts and changing conditions (smooth to rough surface), each stage uses routine mechanics techniques: resolving forces, applying F=ma, and using constant acceleration equations. The multi-stage nature adds some complexity, but the problem-solving is methodical rather than requiring novel insight. |
| Spec | 3.03l Newton's third law: extend to situations requiring force resolution3.03o Advanced connected particles: and pulleys3.03t Coefficient of friction: F <= mu*R model3.03v Motion on rough surface: including inclined planes |
| Answer | Marks | Guidance |
|---|---|---|
| Answer | Marks | Guidance |
| \(T - 0.3g\sin30 = 0.3a\) *OR* \(0.4g\sin30 - T = 0.4a\) | B1 | Either correct N2L for one particle; Putting \(a=0.7\) into correct equation for a single particle and working out \(T\) correctly gets B1M0A0M1A1 |
| \(0.4g\sin30 - 0.3g\sin30 = 0.7a\) | M1 | Allow combined approach as "method", must be components of weight, allow \(mg(\cos/\sin)30\); Consult TL if this is done for both particles |
| \(a = 0.7\) m s\(^{-2}\) AG | A1 | May use the other equation |
| \(T = 0.3g\sin30 + 0.3\times0.7\) | M1 | Allow \(0.3g(\cos/\sin)30\). Accept cv(0.7) |
| \(T = 1.68\) N | A1 |
| Answer | Marks | Guidance |
|---|---|---|
| Answer | Marks | Guidance |
| \(V = 1.8 \times 0.7\) | M1 | Accept cv(0.7) |
| \(V = 1.26\) m s\(^{-1}\) | A1 |
| Answer | Marks | Guidance |
|---|---|---|
| Answer | Marks | Guidance |
| Dec \(= 1.26/1.4\) | M1 | Accept \(1.8\times0.7/1.4\); cv(1.26) |
| Dec \(= 0.9\) m s\(^{-2}\) | A1 | Or \(a = +/-0.9\) |
| Answer | Marks | Guidance |
|---|---|---|
| Answer | Marks | Guidance |
| \(T - 0.3g\sin30 = -0.3\times0.9\) | M1 | N2L, 2 forces including cmpt of weight cv(0.9) but signs must be consistent with the direction of motion; Allow \(mg(\cos/\sin)30\) |
| A1ft | ||
| \(T = 1.2\) | A1 |
| Answer | Marks | Guidance |
|---|---|---|
| Answer | Marks | Guidance |
| \(-0.4\times0.9 = 0.4g\sin30 - T - F_r\) | M1 | N2L, 3 forces including cmpt of weight cv(0.9) and cv(1.2) but signs must be consistent with the direction of motion; Allow \(mg(\cos/\sin)30\) |
| \(-0.4\times0.9 = 0.4g\sin30 - 1.2 - F_r\) | A1ft | |
| \(F_r = 1.12\) N | A1 |
## Question 7:
### Part (i)
| Answer | Marks | Guidance |
|--------|-------|----------|
| $T - 0.3g\sin30 = 0.3a$ *OR* $0.4g\sin30 - T = 0.4a$ | B1 | Either correct N2L for one particle; Putting $a=0.7$ into correct equation for a single particle and working out $T$ correctly gets B1M0A0M1A1 |
| $0.4g\sin30 - 0.3g\sin30 = 0.7a$ | M1 | Allow combined approach as "method", must be components of weight, allow $mg(\cos/\sin)30$; Consult TL if this is done for both particles |
| $a = 0.7$ m s$^{-2}$ AG | A1 | May use the other equation |
| $T = 0.3g\sin30 + 0.3\times0.7$ | M1 | Allow $0.3g(\cos/\sin)30$. Accept cv(0.7) |
| $T = 1.68$ N | A1 | |
### Part (ii)
| Answer | Marks | Guidance |
|--------|-------|----------|
| $V = 1.8 \times 0.7$ | M1 | Accept cv(0.7) |
| $V = 1.26$ m s$^{-1}$ | A1 | |
### Part (iii)
| Answer | Marks | Guidance |
|--------|-------|----------|
| Dec $= 1.26/1.4$ | M1 | Accept $1.8\times0.7/1.4$; cv(1.26) |
| Dec $= 0.9$ m s$^{-2}$ | A1 | Or $a = +/-0.9$ |
### Part (iv)(a)
| Answer | Marks | Guidance |
|--------|-------|----------|
| $T - 0.3g\sin30 = -0.3\times0.9$ | M1 | N2L, 2 forces including cmpt of weight cv(0.9) but signs must be consistent with the direction of motion; Allow $mg(\cos/\sin)30$ |
| | A1ft | |
| $T = 1.2$ | A1 | |
### Part (iv)(b)
| Answer | Marks | Guidance |
|--------|-------|----------|
| $-0.4\times0.9 = 0.4g\sin30 - T - F_r$ | M1 | N2L, 3 forces including cmpt of weight cv(0.9) and cv(1.2) but signs must be consistent with the direction of motion; Allow $mg(\cos/\sin)30$ |
| $-0.4\times0.9 = 0.4g\sin30 - 1.2 - F_r$ | A1ft | |
| $F_r = 1.12$ N | A1 | |
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7\\
\includegraphics[max width=\textwidth, alt={}, center]{8b79facc-e37f-45c3-95c0-9f2a30ca8fe4-4_392_1192_255_424}\\
$A B$ and $B C$ are lines of greatest slope on a fixed triangular prism, and $M$ is the mid-point of $B C . A B$ and $B C$ are inclined at $30 ^ { \circ }$ to the horizontal. The surface of the prism is smooth between $A$ and $B$, and between $B$ and $M$. Between $M$ and $C$ the surface of the prism is rough. A small smooth pulley is fixed to the prism at $B$. A light inextensible string passes over the pulley. Particle $P$ of mass 0.3 kg is fixed to one end of the string, and is placed at $A$. Particle $Q$ of mass 0.4 kg is fixed to the other end of the string and is placed next to the pulley on $B C$. The particles are released from rest with the string taut. $P$ begins to move towards the pulley, and $Q$ begins to move towards $M$ (see diagram).
\begin{enumerate}[label=(\roman*)]
\item Show that the initial acceleration of the particles is $0.7 \mathrm {~m} \mathrm {~s} ^ { - 2 }$, and find the tension in the string.
The particle $Q$ reaches $M 1.8 \mathrm {~s}$ after being released from rest.
\item Find the speed of the particles when $Q$ reaches $M$.
After $Q$ passes through $M$, the string remains taut and the particles decelerate uniformly. $Q$ comes to rest between $M$ and $C 1.4 \mathrm {~s}$ after passing through $M$.
\item Find the deceleration of the particles while $Q$ is moving from $M$ towards $C$.
\item (a) By considering the motion of $P$, find the tension in the string while $Q$ is moving from $M$ towards $C$.\\
(b) Calculate the magnitude of the frictional force which acts on $Q$ while it is moving from $M$ towards $C$.
\section*{END OF QUESTION PAPER}
\section*{OCR \\
Oxford Cambridge and RSA}
\end{enumerate}
\hfill \mbox{\textit{OCR M1 2015 Q7 [15]}}