Where will the forces of Earth and Moon cancel out?

In summary: So in summary, at the point 'r' along the axis, the gravitational forces due to Earth and Moon will cancel each other out.
  • #1
tascja
87
0

Homework Statement


The mass of the moon is 7.35x10^22 kg. At some point between Earth and the Moon, the force of Earth's gravitational attraction on an object is canceled by the Moon's force of gravitational attraction. If the distance between Earth and the Moon (centre to centre) is 3.84x10^5, calculate where this will occur, relative to Earth


Homework Equations


Fg = (G x m1 x m2) / r^2


The Attempt at a Solution


I know you have to make the Earth's gravitational attraction equal the Moon's gravitational attraction (by putting the preceding equation equal to each other). But i don't know where to plug in the 3.84x10^5. Am i looking for the Moon's r? or Earth's r? I am just not too sure about how to go about solving this?
 
Physics news on Phys.org
  • #2
tascja said:
Am i looking for the Moon's r? or Earth's r? I am just not too sure about how to go about solving this?

Neither of them. The 'r' is the distance from the center of either moon or Earth [for your question, you need the answer as the distance from the center of the earth] along the axis joining the moon and the earth. At this distance, the gravitational forces due to the moon and the Earth cancel. Plug in the equation and solve for 'r'.
 
  • #3
I don't get it?? so I am still using: Fg = (G x m1 x m2) / r^2 right? and I am looking for r... but what are my masses then? Earth and... it doesn't give the mass of the object so is it the mass of the moon?
 
  • #4
At any point along the axis.. there will be two forces acting on the particle. One due to the Earth and one due to the moon. The direction of both the forces will be opposite. You need to equate those two forces and the 'r' you find from the equation will be the 'r' you are looking for. This happens because, at the point 'r' where you make the two forces equal, there are 2 forces acting on the particle in opposite directions. As such, they both will cancel each other out and hence there will be no net resultant force.
 

1. What is gravitational attraction?

Gravitational attraction is the force of attraction between two objects with mass. This force is proportional to the masses of the objects and inversely proportional to the square of the distance between them.

2. How does gravitational attraction work?

Gravitational attraction is a fundamental force of nature that causes massive objects to be drawn towards each other. This is due to the curvature of spacetime caused by the presence of mass.

3. What is the formula for calculating gravitational attraction?

The formula for calculating gravitational attraction is F = G(m1m2)/d^2, where F is the force of attraction, G is the gravitational constant, m1 and m2 are the masses of the objects, and d is the distance between them.

4. How does distance affect gravitational attraction?

The force of gravitational attraction decreases as the distance between two objects increases. This is because the inverse square law states that the force is inversely proportional to the square of the distance between the objects.

5. What are some real-world examples of gravitational attraction?

Some examples of gravitational attraction include the orbit of planets around the sun, the moon orbiting around the Earth, and the attraction between objects on Earth due to its mass.

Similar threads

  • Introductory Physics Homework Help
Replies
12
Views
1K
  • Advanced Physics Homework Help
Replies
29
Views
6K
  • Introductory Physics Homework Help
Replies
18
Views
1K
  • Advanced Physics Homework Help
Replies
4
Views
3K
  • Introductory Physics Homework Help
Replies
21
Views
2K
  • Special and General Relativity
2
Replies
58
Views
3K
  • Introductory Physics Homework Help
Replies
5
Views
2K
Replies
6
Views
1K
  • Advanced Physics Homework Help
Replies
17
Views
4K
  • Astronomy and Astrophysics
Replies
33
Views
3K
Back
Top