AQA M3 2013 June — Question 6 12 marks

Exam BoardAQA
ModuleM3 (Mechanics 3)
Year2013
SessionJune
Marks12
PaperDownload PDF ↗
Mark schemeDownload PDF ↗
TopicOblique and successive collisions
TypeOblique collision, vector velocity form
DifficultyStandard +0.3 This is a standard M3 oblique collision question requiring conservation of momentum, coefficient of restitution, and impulse calculation. While it involves vectors and multiple steps, the techniques are routine for this module: decompose velocities, apply conservation perpendicular to line of centres, use Newton's experimental law along the line of centres, and calculate impulse. The 'show that' part (a) guides students through the solution structure, making it slightly easier than average for M3 material.
Spec1.10a Vectors in 2D: i,j notation and column vectors1.10b Vectors in 3D: i,j,k notation6.03b Conservation of momentum: 1D two particles6.03c Momentum in 2D: vector form6.03e Impulse: by a force6.03f Impulse-momentum: relation6.03j Perfectly elastic/inelastic: collisions6.03k Newton's experimental law: direct impact6.03l Newton's law: oblique impacts

6 Two smooth spheres, \(A\) and \(B\), have equal radii and masses 4 kg and 2 kg respectively. The sphere \(A\) is moving with velocity \(( 4 \mathbf { i } - 2 \mathbf { j } ) \mathrm { ms } ^ { - 1 }\) and the sphere \(B\) is moving with velocity \(( - 2 \mathbf { i } - 3 \mathbf { j } ) \mathrm { m } \mathrm { s } ^ { - 1 }\) on the same smooth horizontal surface. The spheres collide when their line of centres is parallel to unit vector \(\mathbf { i }\). The direction of motion of \(B\) is changed through \(90 ^ { \circ }\) by the collision, as shown in the diagram. \includegraphics[max width=\textwidth, alt={}, center]{3a1726d9-1b0c-41de-8b43-56019e18aac1-14_332_1184_566_543}
  1. Show that the velocity of \(B\) immediately after the collision is \(\left( \frac { 9 } { 2 } \mathbf { i } - 3 \mathbf { j } \right) \mathrm { m } \mathrm { s } ^ { - 1 }\).
  2. Find the coefficient of restitution between the spheres.
  3. Find the impulse exerted on \(B\) during the collision. State the units of your answer.

Question 6:
Part (a):
AnswerMarks Guidance
Answer/WorkingMark Guidance
\(j\)-component of \(B\) unchanged: \(-3\mathbf{j}\) retainedB1 \(j\)-component preserved (smooth spheres, line of centres along \(\mathbf{i}\))
Conservation of momentum in \(\mathbf{i}\) direction: \(4(4) + 2(-2) = 4v_A + 2v_B\)M1 CLM along line of centres
\(12 = 4v_A + 2v_{Bi}\)A1 Correct momentum equation
Direction of \(B\) changed by \(90°\): original \(\mathbf{i}\)-component \(= -2\), so after collision \(\mathbf{i}\)-component \(\perp\) original direction requires \(\frac{9}{2}\)M1 Using \(90°\) condition: \((-2)\cdot v_{Bi} + (-3)(-3) = 0\) giving \(v_{Bi} = \frac{9}{2}\)
Velocity of \(B = (\frac{9}{2}\mathbf{i} - 3\mathbf{j})\ \text{ms}^{-1}\)A1 Shown
Part (b):
AnswerMarks Guidance
Answer/WorkingMark Guidance
From momentum: \(4v_{Ai} = 12 - 2(\frac{9}{2}) = 3\), so \(v_{Ai} = \frac{3}{4}\)M1 A1 Finding velocity of \(A\) after collision
\(e = \frac{v_{Bi} - v_{Ai}}{u_{Ai} - u_{Bi}} = \frac{\frac{9}{2} - \frac{3}{4}}{4-(-2)}\)M1 A1 Correct Newton's law of restitution
\(e = \frac{\frac{15}{4}}{6} = \frac{15}{24} = \frac{5}{8}\)A1 Correct value
Part (c):
AnswerMarks Guidance
Answer/WorkingMark Guidance
Impulse on \(B\) = \(m_B(v_B - u_B) = 2\left[(\frac{9}{2}\mathbf{i}-3\mathbf{j})-(-2\mathbf{i}-3\mathbf{j})\right]\)M1 Impulse = change in momentum
\(= 2(\frac{13}{2}\mathbf{i}) = 13\mathbf{i}\)A1 Correct value
Units: \(\text{N s}\)B1 Correct units stated
I can see these are answer space pages (pages 17-20) for Questions 6 and 7 of what appears to be an AQA mechanics exam (P59194/Jun13/MM03). However, these pages only contain blank answer spaces for students to write in — they do not contain any mark scheme content.
To get the mark scheme for this paper, you would need to:
1. Search the AQA website (aqa.org.uk) for the mark scheme for P59194/Jun13/MM03
2. Search for "AQA MM03 June 2013 Mark Scheme"
3. Check revision resource sites that host past paper mark schemes
Would you like me to help you work through the solutions to Question 7 (the aircraft/helicopter interception problem) shown on page 18? I can solve each part showing full working:
- (a)(i) Finding the bearing for \(v_A = 200\) to intercept \(H\)
- (a)(ii) Finding the time to intercept
- (b) Finding the bearing for closest approach when \(v_A = 150\)
Just let me know and I'll work through the mathematics in full.
# Question 6:

## Part (a):

| Answer/Working | Mark | Guidance |
|---|---|---|
| $j$-component of $B$ unchanged: $-3\mathbf{j}$ retained | B1 | $j$-component preserved (smooth spheres, line of centres along $\mathbf{i}$) |
| Conservation of momentum in $\mathbf{i}$ direction: $4(4) + 2(-2) = 4v_A + 2v_B$ | M1 | CLM along line of centres |
| $12 = 4v_A + 2v_{Bi}$ | A1 | Correct momentum equation |
| Direction of $B$ changed by $90°$: original $\mathbf{i}$-component $= -2$, so after collision $\mathbf{i}$-component $\perp$ original direction requires $\frac{9}{2}$ | M1 | Using $90°$ condition: $(-2)\cdot v_{Bi} + (-3)(-3) = 0$ giving $v_{Bi} = \frac{9}{2}$ |
| Velocity of $B = (\frac{9}{2}\mathbf{i} - 3\mathbf{j})\ \text{ms}^{-1}$ | A1 | Shown |

## Part (b):

| Answer/Working | Mark | Guidance |
|---|---|---|
| From momentum: $4v_{Ai} = 12 - 2(\frac{9}{2}) = 3$, so $v_{Ai} = \frac{3}{4}$ | M1 A1 | Finding velocity of $A$ after collision |
| $e = \frac{v_{Bi} - v_{Ai}}{u_{Ai} - u_{Bi}} = \frac{\frac{9}{2} - \frac{3}{4}}{4-(-2)}$ | M1 A1 | Correct Newton's law of restitution |
| $e = \frac{\frac{15}{4}}{6} = \frac{15}{24} = \frac{5}{8}$ | A1 | Correct value |

## Part (c):

| Answer/Working | Mark | Guidance |
|---|---|---|
| Impulse on $B$ = $m_B(v_B - u_B) = 2\left[(\frac{9}{2}\mathbf{i}-3\mathbf{j})-(-2\mathbf{i}-3\mathbf{j})\right]$ | M1 | Impulse = change in momentum |
| $= 2(\frac{13}{2}\mathbf{i}) = 13\mathbf{i}$ | A1 | Correct value |
| Units: $\text{N s}$ | B1 | Correct units stated |

I can see these are answer space pages (pages 17-20) for Questions 6 and 7 of what appears to be an AQA mechanics exam (P59194/Jun13/MM03). However, these pages only contain **blank answer spaces** for students to write in — they do not contain any mark scheme content.

To get the mark scheme for this paper, you would need to:

1. Search the **AQA website** (aqa.org.uk) for the mark scheme for **P59194/Jun13/MM03**
2. Search for **"AQA MM03 June 2013 Mark Scheme"**
3. Check revision resource sites that host past paper mark schemes

Would you like me to help you **work through the solutions** to Question 7 (the aircraft/helicopter interception problem) shown on page 18? I can solve each part showing full working:

- **(a)(i)** Finding the bearing for $v_A = 200$ to intercept $H$
- **(a)(ii)** Finding the time to intercept
- **(b)** Finding the bearing for closest approach when $v_A = 150$

Just let me know and I'll work through the mathematics in full.
6 Two smooth spheres, $A$ and $B$, have equal radii and masses 4 kg and 2 kg respectively. The sphere $A$ is moving with velocity $( 4 \mathbf { i } - 2 \mathbf { j } ) \mathrm { ms } ^ { - 1 }$ and the sphere $B$ is moving with velocity $( - 2 \mathbf { i } - 3 \mathbf { j } ) \mathrm { m } \mathrm { s } ^ { - 1 }$ on the same smooth horizontal surface. The spheres collide when their line of centres is parallel to unit vector $\mathbf { i }$. The direction of motion of $B$ is changed through $90 ^ { \circ }$ by the collision, as shown in the diagram.\\
\includegraphics[max width=\textwidth, alt={}, center]{3a1726d9-1b0c-41de-8b43-56019e18aac1-14_332_1184_566_543}
\begin{enumerate}[label=(\alph*)]
\item Show that the velocity of $B$ immediately after the collision is $\left( \frac { 9 } { 2 } \mathbf { i } - 3 \mathbf { j } \right) \mathrm { m } \mathrm { s } ^ { - 1 }$.
\item Find the coefficient of restitution between the spheres.
\item Find the impulse exerted on $B$ during the collision. State the units of your answer.
\end{enumerate}

\hfill \mbox{\textit{AQA M3 2013 Q6 [12]}}