The same.
You have to lift the center of mass of the water up to the pump either way. Of course if you attach a tight hose to the outlet you save lifting a half meter by releasing the water at ground level rather than .5 meter up.
An Olympic-sized swimming pool is a rectangular prism that is 50m long, 25m wide,
�lled with water to a depth of 1.5m. We are going to pump the water out of the pool
with a pump that is 0.5 meters above the surface of the water. Compare the costs
of draining the pool from the surface of the water versus draining the pool from the
bottom. Note that 1 gallon of gasoline (�$4) can do about 36.75 megajoules of work.
2 answers
total lift if you release water to the atmosphere .5 meter up at the pump = .5 + .75 meters = 1.25 meters
total mass = 1000kg/m^3 * 50*25*1.5 = 1.875 *10^6 kg
total weight = m g = 9.81*1.875*10^6
= 1.84*10^7 Newtons
total work done = weight * distance = 1.84*10^7 *1.25 = 2.23 * 10^7 Joules
2.33 *10^7 /36.75 *10^6 joules/gal
= .634 gal
.634 * 4 $/gal = $2.54
total mass = 1000kg/m^3 * 50*25*1.5 = 1.875 *10^6 kg
total weight = m g = 9.81*1.875*10^6
= 1.84*10^7 Newtons
total work done = weight * distance = 1.84*10^7 *1.25 = 2.23 * 10^7 Joules
2.33 *10^7 /36.75 *10^6 joules/gal
= .634 gal
.634 * 4 $/gal = $2.54
7 answers