What is gravitational force?

Replies

• 

  Kaustubh Katdare

  Gravitational force is basically the force of attraction that exists between any two masses separated by a distance. So there's gravitational force acting between your computer mouse and your keyboard. You and your desk and so on.
  
  This force is directly proportional to the product of the masses and is inversely proportional to the square of the distance between them. Refer to the formula of gravitational force.
  
  Your second question is tricky. There can be several ways where gravitational force may directly or indirectly influence the production of electricity. Tidal energy, for example could be an indirect way of producing electricity due to moon's gravity.
  
  I'd like to have more details on the question/problem/doubt before I can comment further.
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  sksaxena

  The most fundamental application of Gravitational force in producing Electrical energy is :
  
  Hydro Electricity - which is produced when the water is made to fall from large heights, on the blades of a turbine. Gravitational force is solely responsible for the downward velocity of water, attained during the process. As a result of this velocity, water hits the turbine blades with a strong momentum and electricity is produced via generator.
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  Prashant Munshi

  I agree to the definition of gravitational force given by The_Big_K here and also the application of gravitational force to produce electrical energy in the form of tidal wave which is purely a phenomenon in nature related to gravity.
  
  I however doubt if example of Hydro Electricity suggested by sksaxena could be considered. Of course the potential energy of water which turns the turbine is due to gravity and most form of potential energies on earth happens to be due to gravity of earth or gravity is integral part of potential energy "related to the position of various objects." However, how the water has acquired the potential energy? What role gravity has played to provide the water the potential energy it has? Gravity only pulls the water down but does not contribute to imparting this energy to water (raising the water to a height). Water is taken up by the solar energy. Continued or sustained generation of Hydro electricity would not have been possible without solar energy. So I don't agree with hydro electricity as an example of electricity generation through gravity.
• 

  rahul69

  Prashant Munshi

  I agree to the definition of gravitational force given by The_Big_K here and also the application of gravitational force to produce electrical energy in the form of tidal wave which is purely a phenomenon in nature related to gravity.
  
  I however doubt if example of Hydro Electricity suggested by sksaxena could be considered. Of course the potential energy of water which turns the turbine is due to gravity and most form of potential energies on earth happens to be due to gravity of earth or gravity is integral part of potential energy "related to the position of various objects." However, how the water has acquired the potential energy? What role gravity has played to provide the water the potential energy it has? Gravity only pulls the water down but does not contribute to imparting this energy to water (raising the water to a height). Water is taken up by the solar energy. Continued or sustained generation of Hydro electricity would not have been possible without solar energy. So I don't agree with hydro electricity as an example of electricity generation through gravity.

  I think U r confusing Force with Energy, of course it happen due to solar energy, but the force which acts to bring water down to move turbines is Gravity or gravitational force.
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  Ramani Aswath

  Rahul is right. Without gravity there would not even be water in the first place. Granted solar energy supplied the latent heat of vaporization to evaporate water forming clouds that moved inland and fall (again due to gravity in high places.
  acquiring potential energy (Rho x g x H) again purely because of gravity. When this water flows down to the generators through penstock pipes it acquires kinetic energy (V^2/2g) due to gravity, which runs the generator.
  It is gravity that does the work.
• 

  sksaxena

  Prashant Munshi

  I agree to the definition of gravitational force given by The_Big_K here and also the application of gravitational force to produce electrical energy in the form of tidal wave which is purely a phenomenon in nature related to gravity.
  
  I however doubt if example of Hydro Electricity suggested by sksaxena could be considered. Of course the potential energy of water which turns the turbine is due to gravity and most form of potential energies on earth happens to be due to gravity of earth or gravity is integral part of potential energy "related to the position of various objects." However, how the water has acquired the potential energy? What role gravity has played to provide the water the potential energy it has? Gravity only pulls the water down but does not contribute to imparting this energy to water (raising the water to a height). Water is taken up by the solar energy. Continued or sustained generation of Hydro electricity would not have been possible without solar energy. So I don't agree with hydro electricity as an example of electricity generation through gravity.

  lolzz...I will just repeat as said by Rahul 'You have great confusion between Forces and Energy'! Buddy, Forces are only responsible for imparting ANY form of energy to an object. You mentioned about potential...potential...and potential energy, which even shocks me more. It's not Potential BUT Kinetic energy of water, imparted by GRAVITATIONAL FORCE, responsible directly for electricity generation. Potential Energy is there but acts indirectly, which is usually converted to some other form of energy.
  And Iam sorry but believe me, your this question makes no logical sense :
  'What role gravity has played to provide the water the potential energy it has?'
  Who is saying so?
  You said 'Gravity only pulls the water down but does not contribute to imparting this energy to water'! 😲 Man, Gravity is SOLELY responsible for imparting Kinetic Energy to water, to bring it down! Hope this clears.😀
• 

  Prashant Munshi

  I think some of the points in my post were taken in different context than what intended, so I owe an explanation. The post could be long to deal with all the remarks.
  
  I had taken into account the original question " How the electrical energy is produced by gravitational force?"
  
  Of course total energy in the world has remained same due to basic principle "energy can neither be created nor destroyed" and what we see is only transformation of it from one form into other or in the form of work done by it.
  
  I don't think I have been confusing force with energy. Or saying that gravity does not contribute to the generation of electricity in Hydro power plants. I have already said that most potential energies on earth happen to be due to gravity only. And also agree to that, in hydro, the kinetic energy is gained by water due to the gravity because the potential energy is indeed there in water due to gravity only. There would not be kinetic energy in water without potential energy. Kinetic energy is energy in work while potential energy is energy in storage.
  
  #-Link-Snipped-#
  

  And Iam sorry but believe me, your this question makes no logical sense :
  'What role gravity has played to provide the water the potential energy it has?'
  Who is saying so?

  The potential energy, the water has due to its height above the turbine level has not been attributed to it by gravity in hydrogeneration. It is due to the solar energy which converted water into vapours. I agree the rainfall is result of gravitational force as said by #-Link-Snipped-# , but I disagree on the point
  

  this water acquiring potential energy (Rho x g x H) again purely because of gravity.

  Not purely, but in contribution from solar energy.
  
  So in Hydro generation you see a form of energy cycle Water => Solar Energy vaporises water (not due to gravity) => Potential energy to water (due to gravity in storage at a height) => kinetic energy (due to free fall of water under gravity) => turn the turbine => Turn the generator => Electricity.
  
  Now let us take tidal energy being used for generation of electricity. Water => Raised to coastal reservoirs during high tide under the influence of gravity of Moon and the Sun (due to pure gravity is important) => Run down of the water towards turbine when low tide (Again due to pure gravity) => turn the turbine => turn the generator => electricity. So here there is no contribution of anything else but only gravitational force - to lift the water (and impart potential energy to it) and also to run the water down (to impart kinetic energy to it). Hence this example of generation of electricity attributed to gravitational force, appeals to me.
  
  So the difference is Only gravity (in tidal wave) and "Not Only Gravity" (in hydro generation).
• 

  sksaxena

  Reference to #-Link-Snipped-# 's post :
  'Hence this example of generation of electricity attributed to gravitational force, appeals to me.'
  
  Now if the question is which example appeals YOU more, then I raise my hands off this thread. Because I never say what I like more. In Science, things which are valid are valid. To me, both the examples of electricty generation due to gravity are VALID enough.
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  Prashant Munshi

  #-Link-Snipped-#
  

  Now if the question is which example appeals YOU more, then I raise my hands off this thread.

  Dear Friend,
  I think you are taking this discussion too personally, may be because the other of the examples was forwarded by you. Please don't take it personally. It is not war - but merely a technical discussion where we are explaining different point of views to the best of our knowledge / understanding. Probably we are all right or all wrong - it is only god knows what is right as He only created it.
  
  "an example ....appeals to me" is just another way of saying that I consider that as VALID.
  
  Actually there many other scientific phenomenon / dilemmas which could not be still decided on one side - Light is wave or particle? Is the velocity of light same in all directions to support Einstein's base for relativity ? Is really the Bohr's model of an atom valid? There are many of such controversies and they keep on rolling.
  
  So there is no reason for you to quit the discussion. Just try to give some more scientific explanations. Even if you can't or don't want to share an explanation, does not mean you are defeated or something like that. As you have said, I fully agree with your view that "In Science, things which are valid are valid." This is really the last truth and probably from discussion we just are trying to find that. So please carry on...and make it interesting so some more members may participate and extend this.
• 

  rahul69

  Prashant Munshi

  So the difference is Only gravity (in tidal wave) and "Not Only Gravity" (in hydro generation).

  Well here is another attempt to explain it:
  Potential Energy is always due to some underlying force, Take for example a spring, the potential energy on compressing it is due to intermolecular forces. Now in case of potential energy due to height is due to gravitational force.
  For understanding it better consider a hypothetical experiment: If there is no gravity on earth, clearly there will be no Potential Energy due to height, as water will float in air rather than running down. The sun will still be present with its "solar energy". Thus water will be vapourized but it will not cause rain. So overall there would be no hydro electricity.
  Hope it clears the underlying picture😀
• 

  Prashant Munshi

  #-Link-Snipped-# I appreciate the theory of isolation you are applying to provide the explanation. However, you are eliminating the gravitational force from the scene, but the basis of the question itself is gravity - How can we use gravitational force to generate electricity?
  
  The question would not have existed in absence of gravitational force.
  
  Now let us apply the principle of elimination/isolation in a bit different way. Consider the Hydro generation - There is water in the sea, there is earth, there is turbine, there is sun also but without sunshine (light + heat). Now water has to get to the head race (upper side) of the turbine. No sunshine, no vaporization and despite the gravity being present no rains either on plains or mountains. Right? So there is contribution of solar energy (sunshine) to raise the water to a height (head race).
  
  Now let us apply the principle of elimination/ isolation to Tidal generation - There is water in the sea, there is earth, there is turbine, there is Sun also and again without sunshine (let us hypothetically consider it to be a planet), Moon is already a satellite so does not provide any energy of useful level in the form of shine. Now water has to get to the head race and consider it to be a new moon day (the sun and moon on one side of the earth). No shine so no vaporization of water but tidal wave rise purely due to pull of Moon and Sun on earth and water being loose mass of earth is raised in what we call as tidal wave. This raised water we accumulate in a reservoir (head race) and same we release under the low tide (ebb) again under the gravitation pull by the earth and turn the turbine. So water is raised due to gravity, comes down due to gravity.
  
  There is no denial that gravity does contribute in the case of hydro generation, but it collaborates with sunshine which is the cause of raising the water to the head race.
  
  Now let us take another simple analogy - Prashant can lift a weight of 50Kg. So if only Prashant lifts, we call the job is done by Prashant. Now let us add another 50Kg (100Kg which Prashant alone can't lift) to the load and call Rahul to help Prashant. Do we now say only Prashant or Rahul has done the task?
  
  The original question as I interpreted or The_Big_K interpreted is from this point view where we are considering only gravity and no contribution from anything else and so the example of tidal generation suggested by The_Big_K should be the correct answer.
• 

  rahul69

  That is a good explanation, however from your above paragraph, you do believe that both gravitation and solar energy is responsible for hydro electricity. Right??
  As I am fond of analogies😉. Consider this one: some animals eat plants to generate energy, so their energy comes from plants, but plants cannot exist without sun, So u may say that those animals get energy not only from plants but sun too. Note that this is not the case of working together (as in your example of lifting weight), but of the case of working one after other. Sun makes rain, but it doesnot decide whether it will rain on high or low grounds. Low grounds cannot be used for hydroelectricity due to lower potential energy, So if Sun does not have a active role, its Potential energy due to Gravity that count.
• 

  Ramani Aswath

  rahul69

  That is a good explanation, however from your above paragraph, you do believe that both gravitation and solar energy is responsible for hydro electricity. Right??
  Sun makes rain, but it doesnot decide whether it will rain on high or low grounds.

  Rahul, you have hit the nail on the head.
  That is the rub. Sun provides latent heat of vaporization. It has no role in the cloud rising to heights and rain depositing on high grounds, which is solely due to gravity.
  Consider this: If a candle is lit in a satellite, it will go out even if there is enough oxygen in the shell. Why? The carbon dioxide produced is weightless and remains around the flame and douses it.
  On earth, the water vapour produced by solar energy is lighter and so rises. This is purely a gravity based phenomenon. In zero gravity the same amount of water will be vaporized. It will just remain as a blanket over the liquid water.