No, gravity can not be used as an infinite energy source. In fact, strictly speaking, gravity itself can not be used as an energy source at all. You are confusing forces with energy, which are very different things. Energy is a property of objects, such as balls, atoms, light beams, or batteries.
In contrast, forces describe the interaction between objects. Forces are the way that energy is transferred from one object to another when they interact, but forces are not the energy itself. Gravity is a force, so it just provides one way for objects to exchange and transform energy to different states. If I lift a bowling ball to the top of a hill and let it go, the ball falls, speeds up, and seems to gain energy. Isn't this a case of gravity giving energy to the bowling ball?
Again, gravity is just a force, so it just describes how objects interact. The energy that the ball displays as a falling motion came from my muscles when I hefted the bowling ball to the top of the hill, and not from gravity. Gravity just provides a way to temporarily store energy in an object. We call the energy that an object gains when you lift it against a force "potential energy". Here is essentially what is happening; a pendulum starts swinging from some height h and we wish to calculate what the work done by gravity on this pendulum would be everything we need is in the picture below.
We can also find the displacement of the pendulum bob, which is simply the arc length as given by the picture below. This is a basic trigonometric integral, from which you get after evaluating the limits of integration:.
We can still manipulate this equation a little bit by using the following fact from the picture:. From this, we get:. The pendulum may seem like a complicated system, but again, the work done by gravity is just mgh. In the above proof, however, it was worth going through the calculation in explicit detail even though the result may not be too surprising at this point.
Now, the question you may have is; where does this work that the gravitational force does actually go? The answer is that it transforms into kinetic energy for the pendulum bob, which means that its velocity will increase.
The specific amount that the bob gains in kinetic energy will equal the work done by the gravitational force this is just simple energy conservation.
At the bottom, all of the potential energy will have turned into kinetic energy, which means that the work done by gravity is equal to the kinetic energy of the pendulum bob in our case, the bob will start at rest from some height h, so the initial velocity will be zero :. Now, we know that a pendulum is supposed to swing back and forth dynamically, so really this kinetic energy will turn into potential energy again once the pendulum swings back up to its maximum height the maximum height will be the same as the initial starting height!
When satellites are launched into space, they are put into orbit around the Earth where the gravitational force of the Earth keeps them in that orbit. Therefore, does gravity do work on a satellite orbiting the Earth?
Gravity does not do work on a satellite orbiting the Earth in a circular orbit due to the displacement of the satellite being perpendicular to the force of gravity. In an elliptical orbit, however, gravity does do work on a satellite around a small arc, but the total work done around a full orbit is zero.
In a circular orbit, the gravitational force is always pointing to the center of the Earth and the direction of the displacement is always tangential. Now, real orbits are not perfectly circular due to various different factors. Active 3 years, 4 months ago. Viewed 5k times. Improve this question. Thomas Lee Abshier ND 1 1 gold badge 9 9 silver badges 14 14 bronze badges.
In case, system includes ball and earth! The gravitational field was there before the ball was introduced, and will be there after the ball leaves. Both masses have a gravitational field inherent to their mass. The presence of the mass in gravitational field results in a force on both masses.
As long as the ball is in the gravity field, a force will be present, acting on the ball. Add a comment. Active Oldest Votes. Improve this answer. Cort Ammon Cort Ammon 42k 4 4 gold badges 85 85 silver badges bronze badges. But the earth itself is part of the universe. So the ball is a part a bigger system, the universe. So, if we do work on any object, it is stored in the whole system.
If this is so, then what does the concept of an isolated system imply? However, there are cases where they are isolated enough that you can get good predictions out of pretending they were isolated. For example, in this case, the potential energy of the ball is also affected by Jupiter, or even Alpha Cenaturi! However, if you run the numbers for the isolated Earth-ball system and run the numbers for a system with all the stars and planets in it, you find that the stars and other planets have such an extraordinarily weak effect that you almost get the same answer with You can, however, create cases where those little details do matter.
An example is the Lagrange point between the Earth and the moon. A Lagrange point is where the pull of gravity from those two bodies cancel each-other out perfectly. If you were to put a ball at a Lagrange point for the earth and moon, and calculate it with an isolated Earth-ball-moon system, you'd find it should stay still. At the Lagrange point, all of the big effects from the Earth and moon cancel out such that those itty bitty effects from the sun or other planets can actually affect things.
Of course, as the ball falls away from the Lagrange point, towards either the Earth or the moon depending on which way it was perturbed , the two major gravitational effects will no longer perfectly cancel.
Once the ball moves away from that point, it once again is The effect of "the rest of the universe" will once again be small enough that you can get away with the simplification.
Origin of energy where does gravitational force get it's energy to do work upon the ball As Virgo and Cort Ammon's answers explain, when you move the ball away from the Earth you are storing energy in the gravitational field, it is a function of the configuration of objects within that field.
Storage mechanism or - what the heck is this gravity thing anyway? How exactly does gravity work? Why would spacetime curvature cause gravity? Gravity is slightly stronger over places with more mass underground than over places with less mass. Areas in blue have slightly weaker gravity and areas in red have slightly stronger gravity. GRACE detects tiny changes in gravity over time.
These changes have revealed important details about our planet. What Is Gravity? What else does gravity do? Gravity in our universe Gravity is what holds the planets in orbit around the sun and what keeps the moon in orbit around Earth. What is a black hole? More about gravity! What is a gravitational wave? What is a barycenter? If you liked this, you may like: What Is a Barycenter?
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