Math/Physics Problem
(I'd be glad if you solved one of them).

19.2

76.8

Step-by-step explanation:

density × volume = mass

mass = 62.4 × (pi × (40/2)² × h)

mass = 78,374.4h

WD = m×9.8×h = 9.8mh

WD = 768,069.12h²

At h = 5

WD = 768,069.12×5²

= 19,201,728 ft-lb

= 19.2 million ft-lb

At h = 10

WD = 76,806,9.12 × 10²

WD = 76,806,912 ft-lb

= 76.8 million ft-lb

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