it depends on the vapour pressure of the liquid
Gravity. The tower is placed high so that gravity will create pressure and force water through pipes without any mechanical assistance. To give the water potential energy. The water can flow down hill without using pumps. It creats water pressure. Water flows from a higher place to lower place without a pump using only gravity. Once the water levels are the same you'd need a pump to transfer the remainder of H2O. The higher the start the faster the flow ( until you reach the force of gravity) and thus the better pressure coming to your home and faster the shampoo is rinsed out of your hair.
Energy and MassOR, put another way, "does mass have energy"? The answer to both is, "YES". Einstein related the two in his famous equation, E=mc(2). This is the basis for nuclear and thermonuclear reactions in which a small amount of the mass of an element is converted into energy. The relative amounts of mass and energy (radiation) (radiation is only one form of energy) in the universe were fixed in the first moments after the Big Bang, the creation of the universe over 13 billion years ago.
Note: That's just a theory, but today there are many new theories that contradict this in that they postulate that new Universes are being created and destroyed constantly, on a universe sized time scale. These universes can also collide so "new" matter/energy CAN be introduced in to our universe. Think black holes and white holes. Black holes suck matter/energy from our universe and white holes spit it out into new universes. So in essense the "big bang" was really just a white hole and every black hole in our universe is creating a new universe somewhere else. Or so that one theory goes.
False Statement: Under ordinary circumstances, there is no free interconversion of mass and energy. These events can occur only in the environment of tremendous heat and pressure which exists in a star, or, momentarily, in the detonation of a nuclear device.
That statement is completely false but I kept it to demonstrate how poorly the common man understands this concept. You yourself are converting energy to mass and mass to energy at this very moment. Any warm blooded being with some intellect should be able to figure that out.
A simple concept, is a good old fashioned fire in the fireplace. Wood burning turns to heat and light. Wood has more weight before being burned and there's not as much weight left in the ash, true there is some weight lost to out-gassing but it is negligible. So if, Weight equals mass times (the acceleration of) gravity and the weight of ash is less than wood with gravity being a constant, wouldn't you conclude that energy has mass.
SoundSound is a form of energy because energy always carried sound waves.
Essentially, sound is a wave of kinetic energy (a mechanical wave) carried through a medium (air in our everyday experience). Drop a pen on the table in front of you. When the pen hits the table, all the kinetic energy you gave it before dropping it has been converted to other forms of energy. Some is absorbed by the table in the form of heat, and some is absorbed into the pen as heat. Some was absorbed by the air on its way down. The pen may have bounced, and all that movement represents the loss of the original energy. When the pen strikes the table, some of the energy is transmitted to the air as an outward spherical pressure front. The molecules of air continue pushing outward and then retracting back because of the trough of lower pressure that is formed behind it. It is very much like waves in a pond; the wave progresses, but the water itself doesn't move very much. When the expanding front of pressure hits something, some of the energy bounces off, and some is absorbed, depending on the materials and design of the object. Whatever is absorbed is in the form of very small quantities of heat. The sound that you hear when you drop the pen is actually some of the kinetic energy you put into the pen, now converted into sound waves.
Being able to turn electromagnets on and off is what separates them from normal magnets. EX: I recently dismantled a very small remote control car for the battery because it stopped working properly. The front wheels used electromagnets to pull the wheels left or right, a small motor would most likely be too heavy and/or use too much power. EX: In moving pieces in electronics: if it were a normal magnet, it could possibly damage other objects inside of the electronic. EX: Generators. Yes, I said generators. As in, electrical generators. Most rotation-driven electrical generators use magnets -- Something I don't particularly want to explain right now. But anyways, the magnets are a key part in generating electricity. So, if a wire breaks and there's no great way to stop the rotation quickly, just pull the plug on the electromagnets in it and no more juice gets fed into whatever the wire's broken onto, whether it's a person's car, or a nuclear bomb storage area. EX: One of the more commonly known, junkyard cranes! They need some way to release the cars, don't they? Might as well just drop it smack on the ground, it's already in a junkyard anyways. Also wouldn't require people to hook/unhook things. There are probably millions of ways they can be used, you just have to think for a little while.