2 A particle \(P\) of mass 0.5 kg moves in a straight line. At time \(t \mathrm {~s}\) the velocity of \(P\) is \(v \mathrm {~ms} ^ { - 1 }\) and its displacement from a fixed point \(O\) on the line is \(x \mathrm {~m}\). The only forces acting on \(P\) are a force of magnitude \(\frac { 150 } { ( x + 1 ) ^ { 2 } } \mathrm {~N}\) in the direction of increasing displacement and a resistive force of magnitude \(\frac { 450 } { ( x + 1 ) ^ { 3 } } \mathrm {~N}\). When \(t = 0 , x = 0\) and \(v = 20\).
Find \(v\) in terms of \(x\), giving your answer in the form \(v = \frac { A x + B } { ( x + 1 ) }\), where \(A\) and \(B\) are constants to be determined.
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A uniform lamina is in the form of an isosceles triangle \(A B C\) in which \(A C = 2 \mathrm { a }\) and angle \(A B C = 90 ^ { \circ }\). The point \(D\) on \(A B\) is such that the ratio \(D B : A B = 1 : k\). The point \(E\) on \(C B\) is such that \(D E\) is parallel to \(A C\). The triangle \(D B E\) is removed from the lamina (see diagram).
- Find, in terms of \(k\), the distance of the centre of mass of the remaining lamina \(A D E C\) from the midpoint of \(A C\).
When the lamina \(A D E C\) is freely suspended from the vertex \(A\), the edge \(A C\) makes an angle \(\theta\) with the downward vertical, where \(\tan \theta = \frac { 5 } { 18 }\). - Find the value of \(k\).
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Two smooth vertical walls meet at right angles. The smooth sphere \(A\), with mass \(m\), is at rest on a smooth horizontal surface and is at a distance \(d\) from each wall. An identical smooth sphere \(B\) is moving on the horizontal surface with speed \(u\) at an angle \(\theta\) with the line of centres when the spheres collide (see diagram). After the collision, the spheres take the same time to reach a wall. The coefficient of restitution between the spheres is \(\frac { 1 } { 2 }\).