A rectangular tank with a base 4 feet by 5 feet and a height of 4 feet is full of water. The water weighs 62.4 pounds per cubic foot. How much work is done in pumping water out over the top edge in order to empty (a) half of the tank and (b) all of the tank?

(a) 13536.10J

(b) 27072.20J

Step-by-step explanation:

(a) Height of tank (h) = 4 feet = 4/3.2808 = 1.22m

Volume of water in full tank = 4ft*5ft*4ft = 80ft^3

Volume of water in half tank = 1/2 * 80ft^3 = 40ft^3

Density of water = 62.4lb/ft^3

Mass of water = density * volume = 62.4 * 40 = 2496lb = 2496*0.45359kg = 1132.16kg

Work done to empty half of the tank = mgh = 1132.16*9.8*1.22 = 13536.10J

(b) Work done to empty all of the tank = 2 * work done to empty half of the tank = 2 * 13536.10J = 27072.20J