An 18-meter-tall cylindrical tank with a 4-meter radius holds water and is half full. Find the work (in mega-joules) needed to pump all of the water to the top of the tank. (The mass density of water is 1000 kg/m3. Let g = 9.8 m/s2.

W = mgh

W = 226290 x 9.8 x 9

W = 19958778Joules

W = 19.958778MegaJoules

Step-by-step explanation:

Work to full the tank is

W = mgh.

m is the mass of the water.

But density = mass/volume, where volume is the volume of the complete the remaining half full of water to fill the cylindrical tank.

mass = density x volume.

Volume of cylinder = πr2h

Volume to fill the cylinder = (πr2h) / 2. (half of total volume)

Volume = (22x4x4x9) / (7x2). Height used is 18/2 = 9m

Volume = 226.29m3.

Mass = density x volume = 1000 x 226.29 = 226290kg

Therefore, the work is

W = mgh

W = 226290 x 9.8 x 9

W = 19958778Joule = 19.958778MegaJoules