If the force of gravity performs work, and work requires an energy source, what is gravity's?

Question

Hydroelectric power is actually gravitational energy. Where does this energy come from? How is it described by itself alone? Is it being created within all mass at all times, or is it an expendable form of energy? If it is being created in all mass at all times, how does the concept of energy being unable to be created or destroyed remain intact?

Answer 1

gravity only does work when something moves. So if you have water behind a dam and gravity is pulling on it no work is being done.

You can push as hard as you can on a wall and do no work, but pick up a pebble and do pleanty of work.

When dam opens and the water falls gravity still exerts the same force but depending on how far the water falls it does a certian ammount of work.

Gravity is the source of the energy. Or what ever got the water behind the dam was.

Take a 1 kg rock on the floor. It has zero potential energy relative to the floor. Raise the rock one meter and it has one joule of potential energy relative to the floor. You picked up the rock. You are the source of the potential energy. Or you could say the chemical energy in the food you ate was the source.

Release the rock and gravity exerts force on the rock over one meter for 1 joules.Gravity is the source of the Kenitic energy.

If it all seems like we're just making these names up, we are. Or Newton, Watt and Joules did in order to study them. So sometimes identifying the "source" of the energy seems arbitrary, but you just have to learn that the terms in physics have very specific uses and limits.

If your question is how does gravity exert the force on an object over the distance, no one knows. If I throw a ball at your head, obviously I imparted the ball with kenitic energy and sent the energy through the ball into your head.

But if I opened up a trap door under your feet and you immediately fall, how did the Earth tell you to fall towards it? We didn't see anything push or pull you. You just fell through the hole. No one really knows.

There are lots of theories out there, one of the coolest and hardest to understand is Einstein's theory of General Relativity which says a mass (like ) Earth curves space, so objects which would normaly move straight past it, curve into it.

Answer 2

The force of gravity stems from the attraction existing between two massive bodies. If you could concentrate the mass of the earth and the moon at their centers, then the two centers would be attracted toward each other and would not be at rest until the centers were superimposed. The orbital motion of the moon keeps it from approaching the earth (or actually the point on a line between the earth and moon where their combined masses could be considered concentrated).

On earth a steel ball weighing say 100 pounds is attracted toward the center of the earth and is stopped only by the crust of the earth where it exerts 100 pounds of force as on a weighing scale. Although the mass of the steel sphere would always remain constant, the force exerted depends on its distance from the center of the earth, weighing slightly less at the top of a mountain than on a lower valley floor.

Solar energy can heat say a 100 pound sphere of water vaporizing it and making it lighte than surrounding air. The water condenses as it rises up into a cloud (due to its buoyancy) and if you could collect it back into a 100 pound sphere of water (or find substitute water molecules?) it will perform work falling all the way back to earth, moving air to make wind, etc.
There is often a very strong wind as a bad storm cell approaches. Once the water has returned to a damed up lake it can perform even more work falling down through a water turbine to a lower river. Think how much work it could do if it fell from the cloud through a pipe right into the turbine! No energy is created or destroyed. Solar energy raises the water up to a cloud and energy is released as it falls. The water's motion is always regulated by gravity almost as though the sphere of water and the earth were connected by a huge bungie chord (in the absence of gravity). Hope that helps a little.

Answer 3

Between every two bodies there exists a force of attraction. Normally the smaller objects gravitate towards the larger object and this force of attraction is the gravitational pull.

What you need to understand for your question the difference between force and energy. And the various forms of stored energy.

Gravitation is FORCE not energy. Hydroelectric power is a result of potenial and kinetic ENERGY.

Work in this area and your questions will automatically become clear for you.

E = MC2(square) describes the relation between Energy and Mass. Where mass and energy are not destroyed but converted into each another.....based on certain factors...

Answer 4

Such a lot of overly complicated answers!
Hydroelectricity is not "gravitational energy," it is stored solar energy, part of the water cycle (sun heats ocean makes vapor makes clouds moves inland makes rain flows to ocean). Without the solar component keeping the whole water cycle going, hydroelectricity would, ahem, dry up.
The nature of gravity (an effect or a wave or a particle or what) is still being debated, and no experiment has yet proven its nature convincingly.
There is the old question, "If the Sun disappeared, would the Earth immediately begin moving out of orbit or would it take some time for the 'gravity waves' to reach us?" and there is still no definitive answer.
So, bottom line, darn good question. Hydroelectricity doesn't enter into it, but the nature of gravity is a puzzle for sure.

Answer 5

I suppose you could just describe it as a force of attraction (sort of like the atrraction between a proton and electron), not just an unlimited source of energy.

It could be described as not really creating energy spontaneously, but just changing it. For example, if a boulder is sitting on top of a cliff, it has a lot of potential energy. If it falls off, that potential energy becomes kinetic energy, until it stops. Once it stops, the energy has been expended, and it is left in a state with lower potential energy than it started with. This means that in order to regain that energy, work must be done on the boulder.

Hopefully this can account for why gravity is not just an unlimited energy source.

Answer 6

Einstein proposed that the "force" we call gravity is actually a distortion of space caused by the presence of mass. Countless experiments have shown that this is indeed true. Think of the familiar analogy of a thin, flat sheet of rubber. Place a bowling ball on it and a depression forms in the sheet surrounding the ball. The rubber sheet represents space, and the depression represents gravitational energy.

Answer 7

see gravity is nothing but gravitational intensity ie. gravitational field. every mass has a grav. field surrounding it just like electric field around a charge. so grav. field is a energy reservoir
so if we have water at some small height H then it just has P.E.& 0 K.E.wrt. ground level . but when it's allowed to fall freely under gravity then we say grav. field performs -ve work & the P.E. of water gets converted to K.E.
in hydroelectric st. grav. energy gets converted to finally electrical energy

Answer 8

As described by Einstein in his theory of relativity that the space-time dimensions are like a fabric and the planets and stars are laid on this fabric. The fabric bends down due to the weights of the planets/stars/sun. The ditch created in the fabric is in fact gravity, any thing rolls near the ditch-space around the planet falls in the gravity of the planet and keeps on revolving around the planet and bound to stay in the ditch.

Answer 9

Gravity is the force of attraction between two masses based on their respective masses and distance:

Fg = G*m1*m2/R^2

Where G is the gravitational constant 6.67*10^-11, m1 and m2 are the masses, and R is the distance between them.

Answer 10

I think you misunderstand energy conservation.

The energy would be zero when a rock touches the ground. If you lift it from the ground you're ADDING energy to it, in form of potential energy. That energy is released into kinetic energy when you drop it again, falling to the ground where it becomes zero again.