Rod on peg or cylinder

5. \begin{figure}[h] \end{figure} A uniform rod, of weight \(W\) and length \(16 b\), has one end freely hinged to a fixed point \(A\). The rod rests against a smooth circular cylinder, of radius \(5 b\), fixed with its axis horizontal and at the same horizontal level as \(A\). The distance of \(A\) from the axis of the cylinder is 13b, as shown in Figure 2. The rod rests in a vertical plane which is perpendicular to the axis of the cylinder.

1. Find, in terms of \(W\), the magnitude of the reaction on the rod at its point of contact with the cylinder.
2. Show that the resultant force acting on the rod at \(A\) is inclined to the vertical at an angle \(\alpha\) where \(\tan \alpha = \frac { 40 } { 73 }\)
   5 continued \includegraphics[max width=\textwidth, alt={}, center]{54112b4a-3727-4e5b-97e5-4291e7172438-17_81_72_2631_1873}

6. \begin{figure}[h] \end{figure} A plank \(A B\) rests in equilibrium against a fixed horizontal pole. The plank has length 4 m and weight 20 N and rests on the pole at \(C\), where \(A C = 2.5 \mathrm {~m}\). The end \(A\) of the plank rests on rough horizontal ground and \(A B\) makes an angle \(\theta\) with the ground, as shown in
Figure 2. The coefficient of friction between the plank and the ground is \(\frac { 1 } { 4 }\).
The plank is modelled as a uniform rod and the pole as a rough horizontal peg that is perpendicular to the vertical plane containing \(A B\). Given that \(\cos \theta = \frac { 4 } { 5 }\) and that the friction is limiting at both \(A\) and \(C\),

1. find the magnitude of the normal reaction on the plank at \(C\),
2. find the coefficient of friction between the plank and the pole.

5. \begin{figure}[h] \end{figure} A uniform rod \(A B\) of length 8 m and weight \(W\) newtons rests in equilibrium against a rough horizontal peg \(P\). The end \(A\) is on rough horizontal ground. The friction is limiting at both \(A\) and \(P\). The distance \(A P\) is 5 m , as shown in Figure 1. The rod rests at angle \(\theta\) to the horizontal, where \(\tan \theta = \frac { 4 } { 3 }\). The rod is in a vertical plane which is perpendicular to \(P\). The coefficient of friction between the rod and \(P\) is \(\frac { 1 } { 4 }\) and the coefficient of friction between the rod and the ground is \(\mu\).

1. Show that the magnitude of the normal reaction between the rod and \(P\) is \(0.48 W\) newtons.
2. Find the value of \(\mu\).

5. \begin{figure}[h] \end{figure} A uniform rod \(A B\) has length \(8 a\) and weight \(W\).
The end \(A\) of the rod is freely hinged to horizontal ground.
The rod rests in equilibrium against a block which is also fixed to the ground.
The block is modelled as a smooth solid hemisphere with radius \(2 a\) and centre \(D\).
The point of contact between the rod and the block is \(C\), where \(A C = 5 a\) The rod is at an angle \(\theta\) to the ground, as shown in Figure 1.
Points \(A , B , C\) and \(D\) all lie in the same vertical plane.

1. Show that \(A D = \sqrt { 29 } a\)
2. Show that the magnitude of the normal reaction at \(C\) between the rod and the block is \(\frac { 4 } { \sqrt { 29 } } W\) The resultant force acting on the rod at \(A\) has magnitude \(k W\) and acts at an angle \(\alpha\) to the ground.
3. Find (i) the exact value of \(k\) (ii) the exact value of \(\tan \alpha\)
   \includegraphics[max width=\textwidth, alt={}, center]{1732eb73-8c16-4a45-8d3b-a88e659e47ea-15_72_1819_2709_114}

The diagram shows a uniform rod \(A B\), of length \(4 a\) and weight \(W\), resting in equilibrium with its end \(A\) on rough horizontal ground. The rod rests at \(C\) on the surface of a smooth cylinder whose axis is horizontal. The cylinder rests on the ground and is fixed to it. The rod is in a vertical plane perpendicular to the axis of the cylinder and is inclined at an angle \(\theta\) to the horizontal, where \(\cos \theta = \frac { 3 } { 5 }\). A particle of weight \(k W\) is attached to the rod at \(B\). Given that \(A C = 3 a\), show that the least possible value of the coefficient of friction \(\mu\) between the rod and the ground is \(\frac { 8 ( 2 k + 1 ) } { 13 k + 19 }\). Given that \(\mu = \frac { 9 } { 10 }\), find the set of values of \(k\) for which equilibrium is possible.

6. \begin{figure}[h] \end{figure} Figure 5 shows a uniform rod \(A B\) of mass \(M\) and length \(2 a\).

• the rod has its end \(A\) on rough horizontal ground
• the rod rests in equilibrium against a small smooth fixed horizontal peg \(P\)
• the point \(C\) on the rod, where \(A C = 1.5 a\), is the point of contact between the rod and the peg
• the rod is at an angle \(\theta\) to the ground, where \(\tan \theta = \frac { 4 } { 3 }\)

The rod lies in a vertical plane perpendicular to the peg.
The magnitude of the normal reaction of the peg on the rod at \(C\) is \(S\).

1. Show that \(S = \frac { 2 } { 5 } M g\) The coefficient of friction between the rod and the ground is \(\mu\).
   Given that the rod is in limiting equilibrium,
2. find the value of \(\mu\).

4. \begin{figure}[h] \end{figure} A ladder \(A B\) has mass \(M\) and length \(6 a\).
The end \(A\) of the ladder is on rough horizontal ground.
The ladder rests against a fixed smooth horizontal rail at the point \(C\).
The point \(C\) is at a vertical height \(4 a\) above the ground.
The vertical plane containing \(A B\) is perpendicular to the rail.
The ladder is inclined to the horizontal at an angle \(\alpha\), where \(\sin \alpha = \frac { 4 } { 5 }\), as shown in Figure 1.
The coefficient of friction between the ladder and the ground is \(\mu\).
The ladder rests in limiting equilibrium.
The ladder is modelled as a uniform rod.
Using the model,

1. show that the magnitude of the force exerted on the ladder by the rail at \(C\) is \(\frac { 9 M g } { 25 }\)
2. Hence, or otherwise, find the value of \(\mu\).

9 A uniform rod, \(P Q\), of length \(2 a\), rests with one end, \(P\), on rough horizontal ground and a point \(T\) resting on a rough fixed prism of semicircular cross-section of radius \(a\), as shown in the diagram. The rod is in a vertical plane which is parallel to the prism's cross-section. The coefficient of friction at both \(P\) and \(T\) is \(\mu\). \includegraphics[max width=\textwidth, alt={}, center]{691c50b4-50b2-4e3a-a7e0-60f8ec35ee3c-20_451_1093_477_475} The rod is on the point of slipping when it is inclined at an angle of \(30 ^ { \circ }\) to the horizontal. Find the value of \(\mu\).
[0pt] [8 marks] \includegraphics[max width=\textwidth, alt={}, center]{691c50b4-50b2-4e3a-a7e0-60f8ec35ee3c-24_2488_1728_219_141}

4 A rigid thin uniform rod AB with length 2.4 m and weight 30 N is used in different situations.

1. In the first situation, the rod rests on a small support 0.6 m from B and is held horizontally in equilibrium by a vertical string attached to A, as shown in Fig. 4.1. \begin{figure}[h]
   \includegraphics[alt={},max width=\textwidth]{42b6ee17-f0ae-4687-8392-281ba724a607-5_196_707_456_680} \captionsetup{labelformat=empty} \caption{Fig. 4.1}
   \end{figure} Calculate the tension in the string and the force of the support on the rod.
2. In the second situation, the rod rests in equilibrium on the point of slipping with end A on a horizontal floor and the rod resting at P on a fixed block of height 0.9 m , as shown in Fig. 4.2. The rod is perpendicular to the edge of the block on which it rests and is inclined at \(\theta\) to the horizontal. \begin{figure}[h]
   \includegraphics[alt={},max width=\textwidth]{42b6ee17-f0ae-4687-8392-281ba724a607-5_208_746_1101_657} \captionsetup{labelformat=empty} \caption{Fig. 4.2}
   \end{figure} (A) Suppose that the contact between the block and the rod is rough with coefficient of friction 0.6 and contact between the end A and the floor is smooth. Show that \(\tan \theta = 0.6\).
   (B) Suppose instead that the contact between the block and the rod is smooth and the contact between the end A and the floor is rough. The rod is now in limiting equilibrium at a different angle \(\theta\) such that the distance AP is 1.5 m . Calculate the normal reaction of the block on the rod. Calculate the coefficient of friction between the rod and the floor.

8 A ladder has length 4 metres and mass 20 kg The ladder rests in equilibrium with one end on a horizontal surface and the ladder resting on the top of a vertical wall. In this position the ladder is on the point of slipping.
The top of the wall is 1.5 metres above the horizontal surface.
The angle between the ladder and the horizontal surface is \(\alpha\), as shown in the diagram. \includegraphics[max width=\textwidth, alt={}, center]{b0d0c552-71cb-4e5a-b545-de8a9052def0-14_362_863_804_593} The coefficient of friction between the ladder and the wall is 0.5
The coefficient of friction between the ladder and the ground is also 0.5
Show that $$\cos \alpha \sin ^ { 2 } \alpha = \frac { 3 } { 10 }$$ stating clearly any assumptions you make. \includegraphics[max width=\textwidth, alt={}, center]{b0d0c552-71cb-4e5a-b545-de8a9052def0-16_2490_1735_219_139}