Answer:
Step-by-step explanation:
Note answer unit is million lb-ft so its non SI. The lb is lb-force which incorporates the gravity, g.
So the work done is given by lb-force x height.
Height = 100 + 10 (mid-point height of half tank) = 110'
Weight of half tank of water = volume x density
= pi x (10/2)^2 x 20 x 62.4
= 98017.7
Work done = 98017.7*110
= 10781946
= 10.8 million lb-ft
For full tank
Work done = pi x (10/2)^2 x 40 x 62.4 x 120
= 23524245
= 23.5 million lb-ft
