SPS SPS FM Mechanics (SPS FM Mechanics) 2021 September

Question 1
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  1. A car is initially travelling with a constant velocity of \(15 \mathrm {~m} \mathrm {~s} ^ { - 1 }\) for \(T \mathrm {~s}\). It then decelerates at a constant rate for \(\frac { T } { 2 } \mathrm {~s}\), reaching a velocity of \(10 \mathrm {~m} \mathrm {~s} ^ { - 1 }\). It then immediately accelerates at a constant rate for \(\frac { 3 T } { 2 } \mathrm {~s}\) reaching a velocity of \(20 \mathrm {~m} \mathrm {~s} ^ { - 1 }\).
    a Sketch a velocity-time graph to illustrate the motion.
    b Given that the car travels a total distance of 1312.5 m over the journey described, find the value of \(T\).
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  2. A particle \(P\) moves in a straight line. At time \(t \mathrm {~s}\) the displacement \(s \mathrm {~cm}\) from a fixed point \(O\) is given by: \(s = \frac { 1 } { 6 } \left( 8 t ^ { 3 } - 105 t ^ { 2 } + 144 t + 540 \right)\).
    Find the distance between the points at which the particle is instantaneously at rest.
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  3. A cylindrical object with mass 8 kg rests on two cylindrical bars of equal radius. The lines connecting the centre of each of the bars to the centre of the object make an angle of \(40 ^ { \circ }\) to the vertical.
\begin{figure}[h]
\captionsetup{labelformat=empty} \caption{Figure 2} \includegraphics[alt={},max width=\textwidth]{3c44f549-39f9-4b51-9aa3-b918c39c5e5b-06_647_506_333_694}
\end{figure} a Draw a diagram showing all the forces acting on the object. Describe each of the forces using words.
b Calculate the magnitude of the force on each of the bars due to the cylindrical object.
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Question 4
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4. A box \(A\) of mass 0.8 kg rests on a rough horizontal table and is attached to one end of a light inextensible string. The string passes over a smooth pulley fixed at the edge of the table. The other end of the string is attached to a sphere \(B\) of mass 1.2 kg , which hangs freely below the pulley. The magnitude of the frictional force between \(A\) and the table is \(F N\). The system is released from rest with the string taut. After release, \(B\) descends a distance of 0.9 m in 0.8 s . Modelling \(A\) and \(B\) as particles, calculate
a the acceleration of \(B\),
b the tension in the string,
c the value of \(F\).
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Question 5
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5. In this question use \(g = 10 \mathrm {~m} \mathrm {~s} ^ { - 2 }\). A particle of mass 3 kg rests in limiting equilibrium on a rough plane inclined at \(30 ^ { \circ }\) to the horizontal.
a Find the exact value of the coefficient of friction between the particle and the plane. A horizontal force of 36 N is now applied to the particle.
b Find how far down the plane the particle travels after the force has been applied for 4 s .
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