# Calculating Gravitational Potential

• TalliThePrune
In summary, the gravitational potential at point Z, which is 8.10 x 107m away from a planet of mass 1.08 x 1023, is -1.429 x 108 J/kg. This is calculated by adding the gravitational potentials of both the planet and the moon, which are -8.89 x 107 J/kg and -5.93 x 104 J/kg, respectively. The moon's gravity cannot be ignored in this calculation.
TalliThePrune

## Homework Statement

:[/B]
"Calculate gravitational potential at point Z, which is 8.10 x 107m away from a planet of mass 1.08 x 1023. "

(This point is between the planet and a moon, where the gravitational field strength is zero. I'm not sure if that makes a difference. The moon's mass is 4.8 x 1022 and point Z is 5.4 x 107m away from it.).

V = - G M / r

## The Attempt at a Solution

V = - (6.67 x 10^-11) x (1.08 x 10^23) / (8.1 x 10^7)
Therefore
V = - 8.89 x 10^4 J/kg

Is this correct?

- Talli

TalliThePrune said:

## Homework Statement

:[/B]
"Calculate gravitational potential at point Z, which is 8.10 x 107m away from a planet of mass 1.08 x 1023. "

(This point is between the planet and a moon, where the gravitational field strength is zero. I'm not sure if that makes a difference. The moon's mass is 4.8 x 1022 and point Z is 5.4 x 107m away from it.).

V = - G M / r

## The Attempt at a Solution

V = - (6.67 x 10^-11) x (1.08 x 10^23) / (8.1 x 10^7)
Therefore
V = - 8.89 x 10^4 J/kg

Is this correct?

- Talli

Why can you ignore the gravity of the moon?

TalliThePrune
PeroK said:
Why can you ignore the gravity of the moon?

Whoops! Sorry moon. Does this mean I calculate V for both the planet and the moon, and add the two?

So for the moon...
V = - (6.67 x 1011) x (4.8 x 1022) / (5.4 x 107)
V = - 5.93 x 104

Yes. It's good that you wanted to add them and not subtract them!

TalliThePrune
PeroK said:
Yes. It's good that you wanted to add them and not subtract them!

Wonderful! I won't say I didn't consider it for a minute... But that would imply one field disappears with the presence of another, so no!

So VPlanet + Vmoon:
- 5.93 x 104 + - 8.89 x 107 = - 1.429 x 108

Thanks so much for your help.

## What is gravitational potential?

Gravitational potential is the amount of energy that is required to move an object from one location to another in a gravitational field. It is a measure of the potential energy that an object possesses due to its position in the gravitational field.

## How is gravitational potential calculated?

The gravitational potential is calculated using the formula U = -GmM/r, where U is the gravitational potential energy, G is the universal gravitational constant, m and M are the masses of the two objects, and r is the distance between them.

## What is the unit for gravitational potential?

The unit for gravitational potential is joules (J). This is because gravitational potential is a measure of energy, and energy is measured in joules.

## How does distance affect gravitational potential?

As distance increases between two objects, the gravitational potential decreases. This is because the further apart the objects are, the weaker the gravitational force between them becomes, and therefore, the less energy is required to move an object between them.

## Can gravitational potential be negative?

Yes, gravitational potential can be negative. This occurs when the two objects have opposite charges, resulting in a negative value for the gravitational potential energy. However, in most cases, the gravitational potential is positive because the objects have the same charge.

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