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Edexcel M3 Q4
11 marks Challenging +1.2
4. A particle \(P\) of mass \(m \mathrm {~kg}\) moves along a straight line under the action of a force of magnitude \(\frac { k m } { x ^ { 2 } } \mathrm {~N}\), where \(k\) is a constant, directed towards a fixed point \(O\) on the line, where \(O P = x \mathrm {~m} P\) starts from rest at \(A\), at a distance \(a \mathrm {~m}\) from \(O\). When \(O P = x \mathrm {~m}\), the speed of \(P\) is \(v \mathrm {~ms} ^ { - 1 }\).
  1. Show that \(v = \sqrt { \frac { 2 k ( a - x ) } { a x } }\). \(B\) is the point half-way between \(O\) and \(A\). When \(k = \frac { 1 } { 2 }\) and \(a = 1\), the time taken by \(P\) to travel from \(A\) to \(B\) is \(T\) seconds
    Assuming the result that, for \(0 \leq x \leq 1 , \int \sqrt { \frac { x } { 1 - x } } \mathrm {~d} x = \arcsin ( \sqrt { } x ) - \sqrt { } \left( x - x ^ { 2 } \right) +\) constant,
  2. find the value of \(T\). \section*{MECHANICS 3 (A) TEST PAPER 9 Page 2}
Edexcel M3 Q5
13 marks Standard +0.3
  1. A car moves round a circular racing track of radius 100 m , which is banked at an angle of \(4 ^ { \circ }\) to the horizontal.
    1. Show that when its speed is \(8.28 \mathrm {~ms} ^ { - 1 }\), there is no sideways force acting on the car.
      (4 marks)
    2. When the speed of the car is \(12.5 \mathrm {~ms} ^ { - 1 }\), find the smallest value of the coefficient of friction between the car and the track which will prevent side-slip.
    3. The diagram shows a particle \(P\) of mass \(m \mathrm {~kg}\) moving on the inner surface of a smooth fixed hemispherical bowl of radius \(r \mathrm {~m}\) which is fixed with its axis vertical. \(P\) moves at a constant speed in a horizontal circle, at a depth \(h \mathrm {~m}\) below the top of the bowl. \includegraphics[max width=\textwidth, alt={}, center]{9699f53e-366b-4064-af9f-89992c5e93b7-2_254_431_786_1528}
    4. Show that the force \(R\) exerted on \(P\) by the bowl has magnitude \(\frac { m g r } { h } \mathrm {~N}\).
    5. Find, in terms of \(g , h\) and \(r\), the constant speed of \(P\).
    The bowl is now inverted and \(P\) moves on the smooth outer surface at a height \(h\) above the plane face under the action of a force of magnitude \(m g\) applied tangentially as shown. The reaction of the \includegraphics[max width=\textwidth, alt={}, center]{9699f53e-366b-4064-af9f-89992c5e93b7-2_209_355_1224_1636}
    surface of the sphere on \(P\) now has magnitude \(S \mathrm {~N}\).
  2. Given that \(r = 2 h\), prove that \(S < \frac { 1 } { 6 } R\).
Edexcel M3 Q7
15 marks Challenging +1.8
7. A particle \(P\) of mass \(m \mathrm {~kg}\) is fixed to one end of a light elastic string of modulus \(m g \mathrm {~N}\) and natural length \(l \mathrm {~m}\). The other end of the string is attached to a fixed point \(O\) on a rough horizontal table. Initially \(P\) is at rest in limiting equilibrium on the table at the point \(X\) where \(O X = \frac { 5 l } { 4 } \mathrm {~m}\).
  1. Find the coefficient of friction between \(P\) and the table. \(P\) is now given a small displacement \(x \mathrm {~m}\) horizontally along \(O X\), away from \(O\). While \(P\) is in motion, the frictional resistance remains constant at its limiting value.
  2. Show that as long as the string remains taut, \(P\) performs simple harmonic motion with \(X\) as the centre. If \(P\) is held at the point where the extension in the string is \(l m\) and then released,
  3. show that the string becomes slack after a time \(\left( \frac { \pi } { 2 } + \arcsin \left( \frac { 1 } { 3 } \right) \right) \sqrt { \frac { l } { g } } \mathrm {~s}\).
  4. Determine the speed of \(P\) when it reaches \(O\).
Edexcel M3 Q1
6 marks Standard +0.3
  1. A cyclist travels on a banked track inclined at \(8 ^ { \circ }\) to the horizontal. He moves in a horizontal circle of radius 10 m at a constant speed of \(v \mathrm {~ms} ^ { - 1 }\). If there is no sideways frictional force on the cycle, calculate the value of \(v\).
  2. The figure shows a particle \(P\), of mass 0.8 kg , attached to the ends of two light elastic strings. \(A P\) has natural length 20 cm and modulus of elasticity \(\lambda \mathrm { N } . B P\) has natural length 20 cm and modulus of of elasticity \(\mu \mathrm { N } . A\) and \(B\) are fixed to points on the same horizontal \includegraphics[max width=\textwidth, alt={}, center]{627b3411-07ba-4ee4-a672-93a64eeb90b3-1_211_287_726_1704}
    level so that \(A B = 50 \mathrm {~cm}\). When \(P\) is suspended in equilibrium, \(A P =\) 30 cm and \(B P = 40 \mathrm {~cm}\). Calculate the values of \(\lambda\) and \(\mu\).
  3. Suraiya, whose mass is \(m \mathrm {~kg}\), takes a running jump into a swimming pool so that she begins to swim in a straight line with speed \(0.2 \mathrm {~ms} ^ { - 1 }\). She continues to move in the same straight line, the only force acting on her being a resistance of magnitude \(m v ^ { 2 } \sin \left( \frac { t } { 100 } \right) \mathrm { N }\), where \(v \mathrm {~ms} ^ { - 1 }\) is her speed at time \(t\) seconds after entering the pool and \(0 \leq t \leq 50 \pi\).
    1. Find an expression for \(v\) in terms of \(t\).
    2. Calculate her greatest and least speeds during her motion.
    3. A uniform lamina is in the shape of the region enclosed by the coordinate axes and the curve with equation \(y = 1 + \cos x\), as shown.
    4. Show by integration that the centre of mass of the lamina is at a distance \(\frac { \pi ^ { 2 } - 4 } { 2 \pi }\) from the \(y\)-axis.
      (9 marks) \includegraphics[max width=\textwidth, alt={}, center]{627b3411-07ba-4ee4-a672-93a64eeb90b3-1_314_410_1677_1512}
    Given that the centre of mass is at a distance 0.75 units from the \(x\)-axis, and that \(P\) is the point \(( 0,2 )\) and \(O\) is the origin \(( 0,0 )\),
  4. find, to the nearest degree, the angle between the line \(O P\) and the vertical when the lamina is freely suspended from \(P\).
Edexcel M3 Q5
12 marks Challenging +1.8
5. A particle \(P\), of mass 0.5 kg , rests on the surface of a rough horizontal table. The coefficient of friction between \(P\) and the table is \(0.5 . P\) is connected to a particle \(Q\), of mass 0.2 kg , by a light inextensible string passing through \includegraphics[max width=\textwidth, alt={}, center]{627b3411-07ba-4ee4-a672-93a64eeb90b3-1_280_519_2367_1499}
[0pt] [Turn over ... \section*{MECHANICS 3 (A) TEST PAPER 10 Page 2}
  1. continued ...
    a small smooth hole at a point \(O\) on the table, such that the distance \(O Q\) is \(0.4 \mathrm {~m} . Q\) moves in a horizontal circle while \(P\) remains in limiting equilibrium.
    1. Calculate the angle \(\theta\) which \(O Q\) makes with the vertical.
    2. Show that the speed of \(Q\) is \(1.33 \mathrm {~ms} ^ { - 1 }\).
    The motion is altered so that \(Q\) hangs at rest below \(O\) and \(P\) moves in a horizontal circle on the table with speed \(0.84 \mathrm {~ms} ^ { - 1 }\), at a constant distance \(r \mathrm {~m}\) from \(O\) but tending to slip away from \(O\).
  2. Find the value of \(r\).
Edexcel M3 Q6
12 marks Standard +0.8
6. The figure shows a swing consisting of two identical vertical light springs attached symmetrically to a light horizontal cross-bar and supported from a strong fixed horizontal beam. When a mass of 24 kg is placed at the mid- \includegraphics[max width=\textwidth, alt={}, center]{627b3411-07ba-4ee4-a672-93a64eeb90b3-2_200_318_923_1668}
point of the cross-bar, both springs extend by 30 cm to the position \(A\), as shown. Each spring has natural length \(l \mathrm {~m}\) and modulus of elasticity \(\lambda \mathrm { N }\).
  1. Show that \(\lambda = 392 l\). The 24 kg mass is left on the bar and the bar is then displaced downwards by a further 20 cm .
  2. Prove that the system comprising the bar and the mass now performs simple harmonic motion with the centre of oscillation at the level \(A\).
  3. Calculate the number of oscillations made per second in this motion.
  4. Find the maximum acceleration which the mass experiences during the motion.
Edexcel M3 Q7
14 marks Challenging +1.8
7. A particle \(P\) of mass \(m \mathrm {~kg}\) is attached to points \(C\) and \(D\) on the same horizontal level by means of two light inextensible strings \(C P\) and \(D P\), both of length \(40 \mathrm {~cm} . P\) is projected with speed \(u \mathrm {~ms} ^ { - 1 }\) so as to move in a vertical circle in a plane perpendicular to \(C D\), so that angle \(P C D =\) angle \(P D C = \theta\) throughout the motion. \includegraphics[max width=\textwidth, alt={}, center]{627b3411-07ba-4ee4-a672-93a64eeb90b3-2_335_405_1775_1572} If \(u\) is just large enough for the strings to remain taut as \(P\) describes this circular path,
  1. show that \(u ^ { 2 } = 2 g \sin \theta\). The string \(D P\) breaks when \(P\) is at its lowest point. \(P\) then immediately starts to move in a horizontal circle on the end of the string \(C P\).
  2. Prove that \(\tan \theta = \frac { 1 } { 5 } \sqrt { 5 }\).
OCR M3 Q4
11 marks Standard +0.8
4 \includegraphics[max width=\textwidth, alt={}, center]{af1f9f1b-f6c0-4044-9864-5b9ce309d3fa-02_283_711_1754_722} Two uniform smooth spheres \(A\) and \(B\), of equal radius, have masses 5 kg and 2 kg respectively. They are moving on a horizontal surface when they collide. Immediately before the collision, \(A\) has speed \(4 \mathrm {~m} \mathrm {~s} ^ { - 1 }\) and is moving perpendicular to the line of centres, and \(B\) has speed \(4 \mathrm {~m} \mathrm {~s} ^ { - 1 }\) along the line of centres (see diagram). The coefficient of restitution is 0.75 . Find the speed and direction of motion of each sphere immediately after the collision.
OCR M3 Q5
10 marks Challenging +1.2
5 \includegraphics[max width=\textwidth, alt={}, center]{af1f9f1b-f6c0-4044-9864-5b9ce309d3fa-03_462_1109_283_569} Two uniform rods \(A B\) and \(B C\) have weights 64 N and 40 N respectively. The rods are freely jointed to each other at \(B\). The rod \(A B\) is freely jointed to a fixed point on horizontal ground at \(A\) and the rod \(B C\) rests against a vertical wall at \(C\). The rod \(B C\) is 1.8 m long and is horizontal. A particle of weight 9 N is attached to the rod \(B C\) at the point 0.4 m from \(C\). The point \(A\) is 1.2 m below the level of \(B C\) and 3.8 m from the wall (see diagram). The system is in equilibrium.
  1. Show that the magnitude of the frictional force at \(C\) is 27 N .
  2. Calculate the horizontal and vertical components of the force exerted on \(A B\) at \(B\).
  3. Given that friction is limiting at \(C\), find the coefficient of friction between the \(\operatorname { rod } B C\) and the wall.
OCR M3 Q6
14 marks Standard +0.8
6 \includegraphics[max width=\textwidth, alt={}, center]{af1f9f1b-f6c0-4044-9864-5b9ce309d3fa-03_598_839_1480_706} One end of a light inextensible string of length 0.5 m is attached to a fixed point \(O\). A particle \(P\) of mass 0.3 kg is attached to the other end of the string. With the string taut and at an angle of \(60 ^ { \circ }\) to the upward vertical, \(P\) is projected with speed \(2 \mathrm {~ms} ^ { - 1 }\) (see diagram). \(P\) begins to move without air resistance in a vertical circle with centre \(O\). When the string makes an angle \(\theta\) with the upward vertical, the speed of \(P\) is \(v \mathrm {~m} \mathrm {~s} ^ { - 1 }\).
  1. Show that \(v ^ { 2 } = 8.9 - 9.8 \cos \theta\).
  2. Find the tension in the string in terms of \(\theta\).
  3. \(P\) does not move in a complete circle. Calculate the angle through which \(O P\) turns before \(P\) leaves the circular path.
OCR M3 2006 January Q1
7 marks Standard +0.3
1 \includegraphics[max width=\textwidth, alt={}, center]{5bb3bd29-a2eb-4124-802c-fb17b68c50e4-2_246_693_278_731} A particle \(P\) of mass 0.4 kg moving in a straight line has speed \(8.7 \mathrm {~m} \mathrm {~s} ^ { - 1 }\). An impulse applied to \(P\) deflects it through \(45 ^ { \circ }\) and reduces its speed to \(5.4 \mathrm {~m} \mathrm {~s} ^ { - 1 }\) (see diagram). Calculate the magnitude and direction of the impulse exerted on \(P\). \(2 \quad O\) is a fixed point on a horizontal straight line. A particle \(P\) of mass 0.5 kg is released from rest at \(O\). At time \(t\) seconds after release the only force acting on \(P\) has magnitude \(\left( 1 + k t ^ { 2 } \right) \mathrm { N }\) and acts horizontally and away from \(O\) along the line, where \(k\) is a positive constant.
  1. Find the speed of \(P\) in terms of \(k\) and \(t\).
  2. Given that \(P\) is 2 m from \(O\) when \(t = 1\), find the value of \(k\) and the time taken by \(P\) to travel 20 m from \(O\).
OCR M3 2006 January Q3
8 marks Standard +0.3
3 A light elastic string has natural length 3 m . One end is attached to a fixed point \(O\) and the other end is attached to a particle of mass 1.6 kg . The particle is released from rest in a position 5 m vertically below \(O\). Air resistance may be neglected.
  1. Given that in the subsequent motion the particle just reaches \(O\), show that the modulus of elasticity of the string is 117.6 N .
  2. Calculate the speed of the particle when it is 4.5 m below \(O\).
OCR M3 2006 January Q4
10 marks Challenging +1.2
4 \includegraphics[max width=\textwidth, alt={}, center]{5bb3bd29-a2eb-4124-802c-fb17b68c50e4-2_283_711_1754_722} Two uniform smooth spheres \(A\) and \(B\), of equal radius, have masses 5 kg and 2 kg respectively. They are moving on a horizontal surface when they collide. Immediately before the collision, \(A\) has speed \(4 \mathrm {~m} \mathrm {~s} ^ { - 1 }\) and is moving perpendicular to the line of centres, and \(B\) has speed \(4 \mathrm {~m} \mathrm {~s} ^ { - 1 }\) along the line of centres (see diagram). The coefficient of restitution is 0.75 . Find the speed and direction of motion of each sphere immediately after the collision.
OCR M3 2006 January Q5
11 marks Challenging +1.2
5 \includegraphics[max width=\textwidth, alt={}, center]{5bb3bd29-a2eb-4124-802c-fb17b68c50e4-3_462_1109_283_569} Two uniform rods \(A B\) and \(B C\) have weights 64 N and 40 N respectively. The rods are freely jointed to each other at \(B\). The rod \(A B\) is freely jointed to a fixed point on horizontal ground at \(A\) and the rod \(B C\) rests against a vertical wall at \(C\). The rod \(B C\) is 1.8 m long and is horizontal. A particle of weight 9 N is attached to the rod \(B C\) at the point 0.4 m from \(C\). The point \(A\) is 1.2 m below the level of \(B C\) and 3.8 m from the wall (see diagram). The system is in equilibrium.
  1. Show that the magnitude of the frictional force at \(C\) is 27 N .
  2. Calculate the horizontal and vertical components of the force exerted on \(A B\) at \(B\).
  3. Given that friction is limiting at \(C\), find the coefficient of friction between the \(\operatorname { rod } B C\) and the wall.
OCR M3 2006 January Q6
12 marks Standard +0.3
6 \includegraphics[max width=\textwidth, alt={}, center]{5bb3bd29-a2eb-4124-802c-fb17b68c50e4-3_598_839_1480_706} One end of a light inextensible string of length 0.5 m is attached to a fixed point \(O\). A particle \(P\) of mass 0.3 kg is attached to the other end of the string. With the string taut and at an angle of \(60 ^ { \circ }\) to the upward vertical, \(P\) is projected with speed \(2 \mathrm {~ms} ^ { - 1 }\) (see diagram). \(P\) begins to move without air resistance in a vertical circle with centre \(O\). When the string makes an angle \(\theta\) with the upward vertical, the speed of \(P\) is \(v \mathrm {~m} \mathrm {~s} ^ { - 1 }\).
  1. Show that \(v ^ { 2 } = 8.9 - 9.8 \cos \theta\).
  2. Find the tension in the string in terms of \(\theta\).
  3. \(P\) does not move in a complete circle. Calculate the angle through which \(O P\) turns before \(P\) leaves the circular path.
OCR M3 2006 January Q7
16 marks Challenging +1.2
7 \includegraphics[max width=\textwidth, alt={}, center]{5bb3bd29-a2eb-4124-802c-fb17b68c50e4-4_122_1009_265_571} As shown in the diagram, \(A\) and \(B\) are fixed points on a smooth horizontal table, where \(A B = 3 \mathrm {~m}\). A particle \(Q\) of mass 1.2 kg is attached to \(A\) by a light elastic string of natural length 1 m and modulus of elasticity \(180 \mathrm {~N} . Q\) is attached to \(B\) by a light elastic string of natural length 1.2 m and modulus of elasticity 360 N .
  1. Verify that when \(Q\) is in equilibrium \(B Q = 1.5 \mathrm {~m}\). \(Q\) is projected towards \(B\) from the equilibrium position with speed \(u \mathrm {~m} \mathrm {~s} ^ { - 1 }\). Subsequently \(Q\) oscillates with simple harmonic motion.
  2. Show that the period of the motion is 0.314 s approximately.
  3. Show that \(u \leqslant 6\).
  4. Given that \(u = 6\), find the time taken for \(Q\) to move from the equilibrium position to a position 1.3 m from \(A\) for the first time.
OCR M3 2007 January Q1
6 marks Standard +0.3
1 A particle \(P\) of mass 0.6 kg is attached to a fixed point \(O\) by a light inextensible string of length 0.4 m . While hanging at a distance 0.4 m vertically below \(O , P\) is projected horizontally with speed \(5 \mathrm {~m} \mathrm {~s} ^ { - 1 }\) and moves in a complete vertical circle. Calculate the tension in the string when \(P\) is vertically above \(O\).
OCR M3 2007 January Q2
7 marks Standard +0.3
2 \includegraphics[max width=\textwidth, alt={}, center]{f334f6e4-2a60-4647-8b37-e48937c85747-2_231_971_539_587} When a tennis ball of mass 0.057 kg bounces it receives an impulse of magnitude \(I \mathrm {~N} \mathrm {~s}\) at an angle of \(\theta\) to the horizontal. Immediately before the ball bounces it has speed \(28 \mathrm {~m} \mathrm {~s} ^ { - 1 }\) in a direction of \(30 ^ { \circ }\) to the horizontal. Immediately after the ball bounces it has speed \(10 \mathrm {~m} \mathrm {~s} ^ { - 1 }\) in a direction of \(30 ^ { \circ }\) to the horizontal (see diagram). Find \(I\) and \(\theta\).
OCR M3 2007 January Q3
9 marks Standard +0.3
3 \includegraphics[max width=\textwidth, alt={}, center]{f334f6e4-2a60-4647-8b37-e48937c85747-2_465_757_1146_694} Two identical uniform rods, \(A B\) and \(B C\), are freely jointed to each other at \(B\), and \(A\) is freely jointed to a fixed point. The rods are in limiting equilibrium in a vertical plane, with \(C\) resting on a rough horizontal surface. \(A B\) is horizontal, and \(B C\) is inclined at \(60 ^ { \circ }\) to the horizontal. The weight of each rod is 160 N (see diagram).
  1. By taking moments for \(A B\) about \(A\), find the vertical component of the force on \(A B\) at \(B\). Hence or otherwise find the magnitude of the vertical component of the contact force on \(B C\) at \(C\). [3]
  2. Calculate the magnitude of the frictional force on \(B C\) at \(C\) and state its direction.
  3. Calculate the value of the coefficient of friction at \(C\).
OCR M3 2007 January Q4
13 marks Standard +0.3
4 A particle \(P\) of mass 0.2 kg is suspended from a fixed point \(O\) by a light elastic string of natural length 0.7 m and modulus of elasticity \(3.5 \mathrm {~N} . P\) is at the equilibrium position when it is projected vertically downwards with speed \(1.6 \mathrm {~m} \mathrm {~s} ^ { - 1 }\). At time \(t \mathrm {~s}\) after being set in motion \(P\) is \(x \mathrm {~m}\) below the equilibrium position and has velocity \(v \mathrm {~m} \mathrm {~s} ^ { - 1 }\).
  1. Show that the equilibrium position of \(P\) is 1.092 m below \(O\).
  2. Prove that \(P\) moves with simple harmonic motion, and calculate the amplitude.
  3. Calculate \(x\) and \(v\) when \(t = 0.4\).
OCR M3 2007 January Q5
12 marks Standard +0.8
5 The pilot of a hot air balloon keeps it at a fixed altitude by dropping sand from the balloon. Each grain of sand has mass \(m \mathrm {~kg}\) and is released from rest. When a grain has fallen a distance \(x \mathrm {~m}\), it has speed \(v \mathrm {~m} \mathrm {~s} ^ { - 1 }\). Each grain falls vertically and the only forces acting on it are its weight and air resistance of magnitude \(m k v ^ { 2 } \mathrm {~N}\), where \(k\) is a positive constant.
  1. Show that \(\left( \frac { v } { g - k v ^ { 2 } } \right) \frac { \mathrm { d } v } { \mathrm {~d} x } = 1\).
  2. Find \(v ^ { 2 }\) in terms of \(k , g\) and \(x\). Hence show that, as \(x\) becomes large, the limiting value of \(v\) is \(\sqrt { \frac { g } { k } }\).
  3. Given that the altitude of the balloon is 300 m and that each grain strikes the ground at \(90 \%\) of its limiting velocity, find \(k\).
OCR M3 2007 January Q6
12 marks Challenging +1.2
6 \includegraphics[max width=\textwidth, alt={}, center]{f334f6e4-2a60-4647-8b37-e48937c85747-3_446_821_1007_664} Two uniform smooth spheres \(A\) and \(B\) of equal radius are moving on a horizontal surface when they collide. \(A\) has mass 0.4 kg , and \(B\) has mass \(m \mathrm {~kg}\). Immediately before the collision, \(A\) is moving with speed \(4 \mathrm {~m} \mathrm {~s} ^ { - 1 }\) at an acute angle \(\theta\) to the line of centres, and \(B\) is moving with speed \(u \mathrm {~m} \mathrm {~s} ^ { - 1 }\) at \(30 ^ { \circ }\) to the line of centres. Immediately after the collision \(A\) is moving with speed \(v \mathrm {~m} \mathrm {~s} ^ { - 1 }\) at \(45 ^ { \circ }\) to the line of centres, and \(B\) is moving with speed \(3 \mathrm {~m} \mathrm {~s} ^ { - 1 }\) perpendicular to the line of centres (see diagram).
  1. Find \(u\).
  2. Given that \(\theta = 88.1 ^ { \circ }\) correct to 1 decimal place, calculate the approximate values of \(v\) and \(m\).
  3. The coefficient of restitution is 0.75 . Show that the exact value of \(\theta\) is a root of the equation \(8 \sin \theta - 6 \cos \theta = 9 \cos 30 ^ { \circ }\).
OCR M3 2007 January Q7
13 marks Challenging +1.2
7 \includegraphics[max width=\textwidth, alt={}, center]{f334f6e4-2a60-4647-8b37-e48937c85747-4_721_691_269_726} The diagram shows a particle \(P\) of mass 0.5 kg attached to the highest point \(A\) of a fixed smooth sphere by a light elastic string. The sphere has centre \(O\) and radius 1.2 m . The string has natural length 0.6 m and modulus of elasticity \(6.86 \mathrm {~N} . P\) is released from rest at a point on the surface of the sphere where the acute angle \(A O P\) is at least 0.5 radians.
  1. (a) For the case angle \(A O P = \alpha , P\) remains at rest. Show that \(\sin \alpha = 2.8 \alpha - 1.4\).
    (b) Use the iterative formula $$\alpha _ { n + 1 } = \frac { \sin \alpha _ { n } } { 2.8 } + 0.5 ,$$ with \(\alpha _ { 1 } = 0.8\), to find \(\alpha\) correct to 2 significant figures.
  2. Given instead that angle \(A O P = 0.5\) radians when \(P\) is released, find the speed of \(P\) when angle \(A O P = 0.8\) radians, given that \(P\) is at all times in contact with the surface of the sphere. State whether the speed of \(P\) is increasing or decreasing when angle \(A O P = 0.8\) radians.
OCR M3 2008 January Q1
6 marks Moderate -0.8
1 A smooth horizontal surface lies in the \(x - y\) plane. A particle \(P\) of mass 0.5 kg is moving on the surface with speed \(5 \mathrm {~m} \mathrm {~s} ^ { - 1 }\) in the \(x\)-direction when it is struck by a horizontal blow whose impulse has components - 3.5 N s and 2.4 N s in the \(x\)-direction and \(y\)-direction respectively.
  1. Find the components in the \(x\)-direction and the \(y\)-direction of the velocity of \(P\) immediately after the blow. Hence show that the speed of \(P\) immediately after the blow is \(5.2 \mathrm {~m} \mathrm {~s} ^ { - 1 }\). \(P\) is struck by a second horizontal blow whose impulse is \(\mathbf { I }\).
  2. Given that \(P\) 's direction of motion immediately after this blow is parallel to the \(x\)-axis, write down the component of \(\mathbf { I }\) in the \(y\)-direction.
OCR M3 2008 January Q2
9 marks Standard +0.8
2 \includegraphics[max width=\textwidth, alt={}, center]{7e0f600a-18f1-458b-8549-27fca592b19c-2_515_1065_861_541} Two uniform rods \(A B\) and \(B C\), each of length 2 m , are freely jointed at \(B\). The weights of the rods are \(W \mathrm {~N}\) and 50 N respectively. The end \(A\) of \(A B\) is hinged at a fixed point. The rods \(A B\) and \(B C\) make angles \(\tan ^ { - 1 } \left( \frac { 3 } { 4 } \right)\) and \(\beta\) respectively with the downward vertical, and are held in equilibrium in a vertical plane by a horizontal force of magnitude 75 N acting at \(C\) (see diagram).
  1. By taking moments about \(B\) for \(B C\), show that \(\tan \beta = 3\).
  2. Write down the horizontal and vertical components of the force acting on \(A B\) at \(B\).
  3. Find the value of \(W\).