# Newtons laws of universal gravitation

• Queen B
In summary, the gravitational attraction exerted by Earth on the moon is calculated using the equation ag = GM/r^2, where G is the gravitational constant, M is the mass of the Earth or moon, and r is the distance between the two objects. By plugging in the given values, the acceleration is found to be 0.12 m/s^2. To calculate the force, Newton's Second Law of Motion (F=ma) is used, where the mass of the moon would be used since it is experiencing the acceleration. Therefore, the gravitational force exerted by Earth on the moon is 0.12 N.
Queen B

## Homework Statement

its 3.8 x 10^8 from Earth's core to the lunar's core
calculate the gravitational attraction exerted by Earth on the moon

## Homework Equations

ag = GM/ r^2
G= 6.67 x 10^-11
M of earth= 5.98 x 10^24 ... r= 6.37 x 10^6
M of moon= 7.36 x 10^22 ... r= 1.74 X 10^6

## The Attempt at a Solution

ag = ( 6.67 x 10^-11)( 7.36 x 10^22) / ( 6.37 x 10^6) ^2 = 0.12 N
I'm not sure if I'm right or not, I am just really confused as to where I plug in the numbers

Queen B said:

## Homework Statement

its 3.8 x 10^8 from Earth's core to the lunar's core
calculate the gravitational attraction exerted by Earth on the moon

## Homework Equations

ag = GM/ r^2
G= 6.67 x 10^-11
M of earth= 5.98 x 10^24 ... r= 6.37 x 10^6
M of moon= 7.36 x 10^22 ... r= 1.74 X 10^6

## The Attempt at a Solution

ag = ( 6.67 x 10^-11)( 7.36 x 10^22) / ( 6.37 x 10^6) ^2 = 0.12 N
I'm not sure if I'm right or not, I am just really confused as to where I plug in the numbers

When the question asks for the gravitational attraction it is asking for the force. You are calculating the acceleration (toward the centre of mass of the earth-moon system). The units would m/sec^2.

Other than that your answer appears to be correct. Welcome to PF by the way!

AM

Andrew Mason said:
When the question asks for the gravitational attraction it is asking for the force. You are calculating the acceleration (toward the centre of mass of the earth-moon system). The units would m/sec^2.

Other than that your answer appears to be correct. Welcome to PF by the way!

AM

But how would I calculate the force? And thank you.

Queen B said:
But how would I calculate the force? And thank you.

What is Newton's Second Law of Motion?

F=ma, ok i see now but what mass would i use?

Last edited:
If you have calculated the acceleration of the moon caused by the earth, then you would use the mass of the ...?

The Earth?

Try again.

The Moon.

Good job.

1 person

## What is Newton's law of universal gravitation?

Newton's law of universal gravitation states that every object in the universe attracts every other object with a force that is directly proportional to the product of their masses and inversely proportional to the square of the distance between them.

## How did Newton discover this law?

Newton discovered this law while observing the motion of objects on Earth and the motion of celestial bodies in the sky. He also used mathematical calculations and experiments to confirm his observations.

## What are the three laws of motion that are related to Newton's law of universal gravitation?

The three laws of motion related to Newton's law of universal gravitation are:
1. The law of inertia: an object will remain at rest or in motion at a constant velocity unless acted upon by an external force.
2. The law of acceleration: the acceleration of an object is directly proportional to the net force acting on it and inversely proportional to its mass.
3. The law of action and reaction: for every action, there is an equal and opposite reaction.

## Does Newton's law of universal gravitation apply to all objects in the universe?

Yes, Newton's law of universal gravitation applies to all objects in the universe, regardless of their size or mass. However, it is most noticeable in objects with larger masses, such as planets and stars, due to the stronger gravitational forces between them.

## Can Newton's law of universal gravitation be used for objects on Earth?

Yes, Newton's law of universal gravitation can be used to calculate the gravitational force between objects on Earth, such as the force between a person and the Earth or between two objects on the surface of the Earth. However, for objects with smaller masses and closer distances, the effects of gravity may be negligible.

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