1. A 20-ft ladder weighing 65 lb (assumed concentrated at its mid-length) rests on a vertical plane with its lower end on a horizontal floor and its upper end against a vertical wall. The ladder supports a 160-lb person at the top (upper end). The coefficient of static friction at the floor is 0.30 and at the wall is also 0.20. (Note that the location of the 160- lb person in this homework problem is at the very top of the ladder). Show free-body diagram(s) a) Determine the smallest angle that the ladder can make with the floor before slipping begins. b) Determine the frictional force between the floor and the lower end of the ladder.

1. A 20-ft ladder weighing 65 lb (assumed concentrated at its mid-length) rests on a vertical plane with its lower end on a horizontal floor and its upper end against a vertical wall. The ladder supports a 160-lb person at the top (upper end). The coefficient of static friction at the floor is 0.30 and at the wall is also 0.20. (Note that the location of the 160- lb person in this homework problem is at the very top of the ladder). Show free-body diagram(s) a) Determine the smallest angle that the ladder can make with the floor before slipping begins. b) Determine the frictional force between the floor and the lower end of the ladder.

International Edition---engineering Mechanics: Statics, 4th Edition

4th Edition

ISBN:9781305501607

Author:Andrew Pytel And Jaan Kiusalaas

Publisher:Andrew Pytel And Jaan Kiusalaas

Chapter7: Dry Friction

Section: Chapter Questions

Problem 7.72P

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