The problem involves calculating the horsepower required for a pump to raise water from a depth of 50 meters while ejecting it at a flow rate of 2 kg/s and a speed of 10 m/s. The discussion centers around the energy calculations necessary for lifting and accelerating the water.
Participants are actively engaging with the problem, questioning assumptions about the calculations and the relationships between different physical quantities. Some guidance has been provided regarding the need to consider both potential and kinetic energy in the calculations.
There are indications of confusion regarding units and the correct interpretation of flow rate in the context of energy calculations. Participants are encouraged to clarify their understanding of the problem setup and the physical principles involved.
jamesjd said:t = s/v = 5 seconds
m = t/flow rate = 2.5kg
Borek said:Ejection speed is not necessarily the speed at which water travels up. Besides, time you have calculated doesn't matter - each second you have to move 2 kg of water 50 meters up.
jamesjd said:Is it not 10m? erm is the calculation Mass = flow rate/ time?
To be brutally honest, no. You have not followed Borek's advice. I'll repeat it, highlighting the key concept:jamesjd said:Was any of my working correct?
How much energy is needed to lift one kilogram of water 50 meters?Borek said:You need to do two things - transfer water up, and accelerate it to 10 m/s. Calculate energies involved.
D H said:How much energy is needed to lift one kilogram of water 50 meters?
How much energy is needed to make that one kilogram of water move at 10 meters/second?
micuklein said:2*9.81*50=981 Js-1