Question

3. An elevator at Studious University has stopped between the first and second floors. The ca attached to the car wei ghs 5 pounds per foot and is 50 feet long. The car itself weighs 1000 pounds, including two 100 pound students who are trapped inside. To rescue the students, the r must be lifted S Teer by manually winding the cable onto a pulley at the top of the building a. How much work must be done? b. Once the students have been saved, the car must be lifted the remaining 45 feet to the top the building. How much additional work must be done?

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Answer 1

if the pound given in question is mass like slug then multiply by 32.2.

Weight of cable, w_c = 5 pounds/ft total weight, w_c = 5 times 50 feet = 250 pounds weight of car = 1000 pounds weight of students = 200(pounds) (2 students) total weight = 250 + 1000 + 200 = 1450 pounds (a) work = w(h) w_3 = 1450 times 5 feet w_3 = 759 pound foot (b) now h = 45 feet w = 1450 - 200 = 1250 w_j = 1250 times 45 = 56250 pound - feet if the pound given in question is mass like slug then multiply by 32.2.