[67] A uniform ladder 4.0 m long of mass 25 kg rests with its upper end against a smooth
vertical wall and its lower end on rough ground. What must be the least coefficient of friction
between the ground and the ladder for it to be inclined at 60° to the horizontal without
slipping?
[A] tan60/2
[C]
2tan60
[D] 2/tan60
[B] ½ tan60
Space for your working
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