38. (a) how much work is done lifting a 60 pound chair from the ground to the top of a 20 foot
building with a cable which weighs 1 pound per foot?
(b) how much work is done lifting the same chair from the ground to a height of 5 feet with the same
cable?
39. (a) how much work is done lifting a 10 pound calculus book from the ground to the top of a 30 foot
building with a cable which weighs 2 pounds per foot?
(b) from the ground to a height of 10 feet? (c) from a height of 10 feet to a height of 20 feet?
40. how much work is done lifting an 80 pound injured child to the top of a 20 foot hole using a stretcher
weighing 14 pounds and a cable which weighs 1 pound per foot?
42. how much work is done lifting an 120 pound injured adult to the top of a 30 foot hole using a stretcher
weighing 10 pounds and a cable which weighs 2 pound per foot?