# Is the gravitational force higher than it should be?

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• nabil23
In summary, the concept of gravitational potential energy is relative to the chosen reference point. If the reference point is the surface of the planet, then an object at rest has zero gravitational potential energy. However, if the reference point is the center of the planet, then the object will have non-zero gravitational potential energy. The force of gravity is not affected by the choice of reference point, only the potential energy. Additionally, the force exerted by an object on the ground does not depend on its potential energy, but rather its weight.

#### nabil23

does the mass on the surface of the planet (in state of rest ) has inside it the same gravitational energy to a similar mass after a free falling above its surface for one entire second?

Hi and welcome to PF
It's not clear exactly what you want to know but I can tell you that the Gravitational Energy just depends on the Position (height above the reference level) of the mass. If it has already fallen for a second, it will have gained Kinetic Energy and will have less Gravitational Potential Energy than where it started.
Ignoring energy lost by friction through the air, the sum of the GPE and the KE will be the same.

nabil23 said:
does the mass on the surface of the planet (in state of rest ) has inside it the same gravitational energy...

Gravitational potential energy is relative so it depends where your reference is. If your reference is the surface of the Earth then it will have zero gravitational potential energy. If your reference is the centre of the Earth it will be non zero.

..to a similar mass after a free falling above its surface for one entire second?

While it falls its gravitational potential energy will reduce. The absolute value at any time depends on its height at that time. It will only have the same gravitational potential energy when it's also on the surface.

If the reference is the surface of the Earth, the mass will have zero gravitational energy ? so how the mass on the surface of the Earth cause pressure to the interior? it must have the energy to cause pressure.

nabil23 said:
If the reference is the surface of the Earth, the mass will have zero gravitational energy ? so how the mass on the surface of the Earth cause pressure to the interior? it must have the energy to cause pressure.
Well, first you are taking the reference point to be the surface of the Earth and are correctly stating that it has zero potential energy relative to that position, THEN you are taking the reference point as being the center of the Earth and you are complaining that it has potential energy relative to THAT reference point, which of course it does. You need to make up your mind what your reference point is.

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nabil23 said:
If the reference is the surface of the Earth, the mass will have zero gravitational energy ? so how the mass on the surface of the Earth cause pressure to the interior? it must have the energy to cause pressure.
I said that on the surface it has zero gravitational potential _energy_ relative to the surface. The gravitational _force_ is not zero.

Work (or energy) = force * distance

The distance between the surface and the surface is zero (obviously).

The force is not zero.

If the reference was a cloud at 1000m the object on the surface would have negative gravitational potential energy.

There may be a bit of a language barrier at work here. I notice that the OP asked about “gravitational energy “, and all responses have been about “gravitational potential energy “. Nabil23, let me see if I understand your latest post correctly. You are observing that an object on the ground exerts pressure against the ground, and you are asking how it can exert a force if it has no energy, and the source of that energy is apparently gravity, right?

So the main questions to ask would be, “does an object with weight exert a force against the ground beneath it?”, “is energy required in order to exert a force?”, and “if so, what is the source of that energy?”. Does that sound right to you?

nabil23

## 1. Is the gravitational force higher than it should be?

This is a commonly asked question among people who are curious about the laws of gravity. The answer is yes, the gravitational force is higher than it should be due to the concept of gravitational acceleration. This acceleration is caused by the mass of an object and the distance between two objects.

## 2. How is the gravitational force measured?

The gravitational force is measured using the universal gravitational constant, also known as G. This constant is used in the equation F = G(m1m2)/r^2, where m1 and m2 are the masses of the two objects and r is the distance between them.

## 3. Does the gravitational force vary on different planets?

Yes, the gravitational force varies on different planets due to their different masses and sizes. For example, the gravitational force on Earth is higher than on the Moon because Earth has a larger mass and size compared to the Moon.

## 4. Can the gravitational force be manipulated?

No, the gravitational force cannot be manipulated as it is a fundamental force of nature. Although, the effects of gravity can be counteracted by other forces, such as the centrifugal force or the electromagnetic force.

## 5. How does the distance between two objects affect the gravitational force?

The distance between two objects directly affects the gravitational force between them. As the distance between two objects increases, the gravitational force decreases. This is because the force of gravity follows an inverse square law, meaning that the force decreases by the inverse of the square of the distance between the objects.