Consider a roong contractor is pulling on a rope to raise a load of roof shingles as shown. The contractor is standing on a roof with a pitch of 15 degrees. Each bundle of shingles weighs 30 lbs and the platform that carries the shingles weighs 20 lbs.
(a) Draw a Free Body Diagram and Vector Diagram for the Contractor and the platform carrying the shingles.
(b) How many packs of shingles can the contractor lift before he begins to slide down the roof assuming the following Contractor weights and values for the coecient of static friction exists between the contractor and the roof?
Scenario muS Weight of Contractor
(1) 0.2 [-] 160 [lbs]
(2) 0.2 [-] 280 [lbs]
(3) 0.55 [-] 160 [lbs]
(4) 0.55 [-] 280 [lbs]