A 70 kg painter holding a 15 kg paint is climbing up a 30 m-long ladder, which weighs 20 kg, against a frictionless wall at an angle of 60 degree.
(a) What is the minimum value of the static friction coecient that prevents the ladder from slipping when the painter is at 20m up along the ladder?
(b) If s = 0.01, how far could the painter go up along the ladder?