AQA M3 2015 June — Question 5 11 marks

Exam BoardAQA
ModuleM3 (Mechanics 3)
Year2015
SessionJune
Marks11
PaperDownload PDF ↗
Mark schemeDownload PDF ↗
TopicOblique and successive collisions
TypeOblique collision, find velocities/angles
DifficultyChallenging +1.2 This is a standard M3 oblique collision problem requiring resolution of velocities along/perpendicular to the line of centres, conservation of momentum in the line of centres, and Newton's restitution equation. While it involves multiple steps and careful bookkeeping with given trigonometric values, it follows a well-established procedure taught explicitly in M3 with no novel insight required. The 11 marks reflect computational length rather than conceptual difficulty, placing it moderately above average difficulty.
Spec6.03c Momentum in 2D: vector form6.03d Conservation in 2D: vector momentum6.03k Newton's experimental law: direct impact

5 Two smooth spheres, \(A\) and \(B\), have equal radii and masses 2 kg and 1 kg respectively. The spheres move on a smooth horizontal surface and collide. As they collide, \(A\) has velocity \(4 \mathrm {~m} \mathrm {~s} ^ { - 1 }\) in a direction inclined at an angle \(\alpha\) to the line of centres of the spheres, and \(B\) has velocity \(2.6 \mathrm {~m} \mathrm {~s} ^ { - 1 }\) in a direction inclined at an angle \(\beta\) to the line of centres, as shown in the diagram.
The coefficient of restitution between \(A\) and \(B\) is \(\frac { 4 } { 7 }\).
Given that \(\sin \alpha = \frac { 4 } { 5 }\) and \(\sin \beta = \frac { 12 } { 13 }\), find the speeds of \(A\) and \(B\) immediately after the collision.
[0pt] [11 marks]

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5 Two smooth spheres, $A$ and $B$, have equal radii and masses 2 kg and 1 kg respectively. The spheres move on a smooth horizontal surface and collide. As they collide, $A$ has velocity $4 \mathrm {~m} \mathrm {~s} ^ { - 1 }$ in a direction inclined at an angle $\alpha$ to the line of centres of the spheres, and $B$ has velocity $2.6 \mathrm {~m} \mathrm {~s} ^ { - 1 }$ in a direction inclined at an angle $\beta$ to the line of centres, as shown in the diagram.\\
\begin{tikzpicture}[
    >=Straight Barb, % Use a simple V-shaped arrowhead to match the image
    velocity/.style={
        postaction={decorate},
        decoration={
            markings,
            mark=at position 0.55 with {\arrow{>}}
        }
    }
]

    % Define the centers of the two circles
    \coordinate (A) at (0,0);
    \coordinate (B) at (2,0);

    % Draw the dashed line of centres
    \draw[densely dashed] (-2.2, 0) -- (4.2, 0) node[right, text=black] {\textsf{Line of centres}};

    % Draw the two touching circles
    \draw (A) circle (1);
    \draw (B) circle (1);

    % Add labels A and B below the circles
    \node at (0, -1.4) {$A$};
    \node at (2, -1.4) {$B$};

    % --- Particle A ---
    \def\angleA{115} % Angle for velocity vector A
    
    % Draw velocity vector A
    \draw[velocity] (\angleA:2.8) -- (A);
    \node[right, xshift=2pt] at (\angleA:2.2) {$4\mathrm{\,m\,s^{-1}}$};

    % Draw angle arc and label for alpha
    \draw (180:0.5) arc (180:\angleA:0.5);
    \node at (147.5:0.75) {$\alpha$};


    % --- Particle B ---
    \def\angleB{100} % Steeper angle for velocity vector B
    
    % Draw velocity vector B
    \draw[velocity] ($(B) + (\angleB:2.8)$) -- (B);
    \node[right, xshift=2pt] at ($(B) + (\angleB:2.2)$) {$2.6\mathrm{\,m\,s^{-1}}$};

    % Draw angle arc and label for beta
    \draw ($(B) + (180:0.5)$) arc (180:\angleB:0.5);
    \node at ($(B) + (140:0.75)$) {$\beta$};

\end{tikzpicture}

The coefficient of restitution between $A$ and $B$ is $\frac { 4 } { 7 }$.\\
Given that $\sin \alpha = \frac { 4 } { 5 }$ and $\sin \beta = \frac { 12 } { 13 }$, find the speeds of $A$ and $B$ immediately after the collision.\\[0pt]
[11 marks]

\hfill \mbox{\textit{AQA M3 2015 Q5 [11]}}