7 A uniform ladder \(A B\), of length 6 metres and mass 22 kg , rests with its foot, \(A\), on rough horizontal ground. The ladder rests against the top of a smooth vertical wall at the point \(C\), where the length \(A C\) is 5 metres. The vertical plane containing the ladder is perpendicular to the wall, and the angle between the ladder and the ground is \(60 ^ { \circ }\). A man, of mass 88 kg , is standing on the ladder. The man may be modelled as a particle at the point \(D\), where the length of \(A D\) is 4 metres. The ladder is on the point of slipping.
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1. Draw a diagram to show the forces acting on the ladder.
2. Find the coefficient of friction between the ladder and the horizontal ground.
   [0pt] [6 marks]
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