申論題

1. A 10 kg uniform ladder 25 m long rests against a smooth wall as shown in Fig* L An 80 kg man S climbs up the ladder to a point A,- a distance I＞2.0 m from the bottom of the ladder, before the I ladder slips. What is the coefficient of friction between the ladder and the ground if the angle 1 between the ladder and ground is 60° ? (25%