| Exam Board | OCR MEI |
|---|---|
| Module | Further Mechanics B AS (Further Mechanics B AS) |
| Year | 2022 |
| Session | June |
| Marks | 10 |
| Paper | Download PDF ↗ |
| Mark scheme | Download PDF ↗ |
| Topic | Centre of Mass 1 |
| Type | Composite solid with hemisphere and cylinder/cone |
| Difficulty | Standard +0.8 This is a multi-part Further Maths mechanics question requiring volume of revolution integration, centre of mass calculations for composite solids, and toppling analysis. Part (a) requires detailed proof using integration by parts or similar techniques. While the individual techniques are standard for FM students, the combination of calculus-based COM, composite body analysis, and toppling condition makes this moderately challenging, though still within expected FM scope. |
| Spec | 4.08d Volumes of revolution: about x and y axes6.04c Composite bodies: centre of mass6.04d Integration: for centre of mass of laminas/solids6.04e Rigid body equilibrium: coplanar forces |
| Answer | Marks | Guidance |
|---|---|---|
| 3 | (a) | [ 202 ππ₯Μ =] πβ«π₯(π₯2+3)2dπ₯ |
| 5 | M1 | 3.1b |
| = πβ«(π₯5+6π₯3+9π₯) | A1 | 1.1 |
| Answer | Marks | Guidance |
|---|---|---|
| 0 | M1 | 1.1 |
| Answer | Marks |
|---|---|
| 5 6 4 2 3 | Must be seen β or equivalent |
| Answer | Marks | Guidance |
|---|---|---|
| 303 | A1 | 1.1 |
| Answer | Marks |
|---|---|
| (b) | 202 1001 |
| Answer | Marks | Guidance |
|---|---|---|
| 5 303 | M1 | 3.1b |
| 1 2 | Do not need LHS here | |
| A1 | 1.1 | For both masses correct |
| A1 | 1.1 | For both distances correct |
| π₯Μ = 2.59 | A1 | 1.1 |
| Answer | Marks | Guidance |
|---|---|---|
| (c) | 2.59tan30Β° = 1.495β¦ | M1 |
| Answer | Marks |
|---|---|
| inverseβ¦ | π‘βπππ 2.59 |
| Answer | Marks | Guidance |
|---|---|---|
| This is less than 3 , so does not topple | A1FT | 2.2a |
| Answer | Marks |
|---|---|
| arctan(3/2.59β¦)=49.155β¦o | FT correct method to |
Question 3:
3 | (a) | [ 202 ππ₯Μ
=] πβ«π₯(π₯2+3)2dπ₯
5 | M1 | 3.1b | DR in part (a)
= πβ«(π₯5+6π₯3+9π₯) | A1 | 1.1
1 6 9 2
= π[ π₯6+ π₯4+ π₯2]
6 4 2
0 | M1 | 1.1 | Use of limits and at least one term
correct on ft
202 64 96 36 158
ππ₯Μ
= π( + + )[= ]
5 6 4 2 3 | Must be seen β or equivalent
395
π₯Μ
=
303 | A1 | 1.1 | AG
[4]
(b) | 202 1001
(58.4πΓπ₯Μ
) = 18πΓ1+ πΓ
5 303 | M1 | 3.1b | For attempting ππ₯ +ππ₯
1 2 | Do not need LHS here
A1 | 1.1 | For both masses correct | Do not need LHS here
A1 | 1.1 | For both distances correct | Do not need LHS here
π₯Μ
= 2.59 | A1 | 1.1 | 2.5936 Accept 2.6 | Must come from 58.4πΓπ₯Μ
on LHS
[4]
(c) | 2.59tan30Β° = 1.495β¦ | M1 | 3.1b | 3
Or by finding tanπ = or
π‘βπππ 2.59
inverseβ¦ | π‘βπππ 2.59
Allow tanπ = for
3
M1
This is less than 3 , so does not topple | A1FT | 2.2a | β¦and correct deduction
Note: angle of toppling is
arctan(3/2.59β¦)=49.155β¦o | FT correct method to
incorrect CoM
[2]
3 Fig. 3.1 shows the curve with equation $y = x ^ { 2 } + 3$. The region $R$, shown shaded, is bounded by the curve, the $x$-axis, the $y$-axis and the line $x = 2$. A uniform solid of revolution S is formed by rotating the region R through $2 \pi$ about the $x$-axis.
The volume of $S$ is $\frac { 202 } { 5 } \pi$.
\begin{figure}[h]
\begin{center}
\includegraphics[alt={},max width=\textwidth]{feb9a438-26b0-41d3-b044-6acd6efccde0-3_392_547_511_246}
\captionsetup{labelformat=empty}
\caption{Fig. 3.1}
\end{center}
\end{figure}
\section*{(a) In this question you must show detailed reasoning.}
Show that the $x$-coordinate of the centre of mass of S is $\frac { 395 } { 303 }$.
S is fixed to a cylinder of base radius 3 units and height 2 units to form the uniform solid D . The smaller circular face of S is joined to the top circular face of the cylinder, as shown in Fig. 3.2.
\begin{figure}[h]
\begin{center}
\includegraphics[alt={},max width=\textwidth]{feb9a438-26b0-41d3-b044-6acd6efccde0-3_394_556_1491_244}
\captionsetup{labelformat=empty}
\caption{Fig. 3.2}
\end{center}
\end{figure}
(b) Find the distance of the centre of mass of D from its smaller circular face.
D is placed with its smaller circular face in contact with a rough plane which is inclined at an angle of $30 ^ { \circ }$ to the horizontal. It is given that D does not slip.\\
(c) Determine whether D topples.
\hfill \mbox{\textit{OCR MEI Further Mechanics B AS 2022 Q3 [10]}}