Recent content by jbriggs444

What is the stroke distance? That is, what is the height difference between the piston at the bottom of a stroke and the piston at the top? From the drawings, it looks like about 0.1 meters. That means that you will be drawing up about 1 meter2 times 0.1 meters = 0.1 m3 of water with each...

Yes. I think that everyone here understands that. You want the total of: 1. The force of water pressure on the bottom surface of the top piston ##F_{3bt}## plus... 2. The force of water pressure on the top surface of the bottom piston ##F_{3tb}## plus... 3. The force of water pressure on the...

I do not disagree with this at all. If we are working with absolute pressures and ignoring surface tension then water pressure is always positive. There is no such thing as a suction force pulling anything. However, I am willing to look past that issue and assume that we are instead talking...

For a massless piston assembly subject to no external forces other than water pressure, the calculation for ##F_3## is immediate and obvious. ##F_3 = 0## It cannot be otherwise since the momentum of the piston assembly is constant and zero. That is manifestly incorrect. When summing forces it...

You are seeking to design a pump? It is indeed quite challenging to design a pump that raises water without requiring power.

There are forces other than gravity acting on it. I listed a bunch of constraints on the water. No. That is not the correct result. You will need to explain your reasoning in more detail. In particular, explain why you think that the 0.1 m2 check valve area is relevant. A useful way to proceed...

What freely falling water? I see no freely falling water. I see water constrained by cylinder walls, a piston assembly, a cylinder bottom and a nozzle. It exerts an upward force on one piston and an equal downward force on the other. The water in the 4 meter tube does not move, even after the...

You have not described the situation adequately. Are we to assume that the piston assembly is held in place until a preset moment when it is released? Edit: I think this is what you have in mind. Your expectation is that the piston assembly will descend and that water will squirt out through...

Did you mean to say that ##F_3## is the resultant force exerted by water on the assembly that includes both pistons? That is to say that ##F_3## will be the sum of the forces from water pressure on each of the three piston surfaces. It would have been cleaner phrasing if you said that "##F_1##...

If the pistons were motionless in equilibrium with some external force (as I had supposed), no water would flow. So the check valve permits a one way flow - allowing water out but not air in. You had not stated that the pistons move. It would be good to state that when posing the problem. Do...

I agree that the downward force (suction) from the water on the first piston (##F_1##) is 50000 N. I agree that the upward force (suction) from the water on the check second piston (##F_2##) is 4000 N. Before we can calculate ##F_3## we need to decide what ##F_3## is. Is it the force of...

It would be easy to read this as saying that unproficient students is a solved problem. That the solution is called "special education" and that this solution has been in place for decades. But I know that you stopped short of calling special ed a solution. You only characterized it as an...

For us (1960's and 70's midwest US) it was a three month vacation from June through August. My parents were both teachers, so the entire family had three months each year not tied down by anything. We spent the first three weeks of each summer picking a direction, hopping into the car and...

My training as a network engineer (retired) has been activated... On the face of it, the URL (http://sodwana.uni-ak.ac.at/geom/mitarbeiter/odehnal/talk/innsbruck_2014.pdf) is for plaintext HTTP. And indeed, a plaintext HTTP request does result in the PDF being retrieved. However, one can see...

If one is talking about hand held ballistic projectile weaponry then there is not a lot of room for improvement over gunpowder and lead. Chemical power source with built in oxidizer and projectile in a compact cartridge format offering a rate of fire good enough to deplete reasonable ammo...