How to explain there cannot be a case where r=0 in F=G(Mm/r^2)

  • Thread starter WaaWaa Waa
  • Start date
  • Tags
    Explain
In summary: Classical physics is the theory that relies on the laws of mathematics and physics that we know and understand from everyday life. It's the theory that we use when we want to predict the future behavior of things like planets, balls, and cars. In summary, the member's question is asking about a case where the gravitational force between two point masses is zero. However, according to classical physics, this cannot happen. Instead, when two point masses are separated by a distance r, the gravitational force between them is given by F=GMm/r2. If r=0, then the two point masses are no longer separate and gravity would be infinite.
  • #1
WaaWaa Waa
12
0
Hi. This is my first post here. In one of our science groups in Facebook, a member is asking about a case where r=0 in Newton's Equation F=G(Mm/r^2)

The best i could do was to state that there cannot be two point masses with a distance r=0 between them. He seems to accept my explanation but his intuition that it should be 'infinity' still remains. I would like to explain it better. Can you please help?

I have searched the site but could not find the answer. If there is already a thread, I would be glad if you could point me towards it.
 
Physics news on Phys.org
  • #2
The gravitational force of attraction between two point masses, M & m2, separated by a distance 'r' is given by:

F= GMm/r2

If r=0, then you don't have two masses anymore but one mass. In which cases, gravity would vary with depth of the planet. Read more here.
 
  • #3
WaaWaa Waa said:
Hi. This is my first post here. In one of our science groups in Facebook, a member is asking about a case where r=0 in Newton's Equation F=G(Mm/r^2)

The best i could do was to state that there cannot be two point masses with a distance r=0 between them. He seems to accept my explanation but his intuition that it should be 'infinity' still remains. I would like to explain it better. Can you please help?

I have searched the site but could not find the answer. If there is already a thread, I would be glad if you could point me towards it.

When r=0, you no longer have two masses, you have one. This condition actually does occur at a black hole, where all mass is (believed to be) contained in a singularity, i.e., a single point.
 
  • #4
I don't think the gravity law works well on a quantum scale since the nuclear forces and electromagnetic forces become very strong at small distances.
 
  • #5
Thank you guys for your insights, we managed to resolve the question.

When we are talking about classical physics, I think we sometimes tend to grab ideas from Relativity and Quantum Mechanics and get confused and this seems to be the root of the problem.
 
Last edited:

1. Why can't r ever equal 0 in the equation F=G(Mm/r^2)?

In this equation, r represents the distance between two objects, such as the distance between the Earth and the Sun. If r were to equal 0, it would mean that the two objects are on top of each other, which is physically impossible. Therefore, r can never equal 0 in this equation.

2. What would happen if r were to equal 0 in the F=G(Mm/r^2) equation?

If r were to equal 0 in this equation, the denominator (r^2) would become 0, which would result in the equation being undefined. This means that the force between the two objects would also be undefined.

3. Is there any scenario in which r could theoretically equal 0 in the F=G(Mm/r^2) equation?

No, as mentioned before, r represents the distance between two objects. Since objects cannot occupy the same space, r can never equal 0 in this equation.

4. Are there any other equations or situations where r cannot equal 0?

Yes, in many equations involving distance, time, or other physical quantities, r cannot equal 0. For example, the equation for the force of gravity (F=GMm/r^2) is similar to the equation for the electric force (F=kQq/r^2), where r also cannot equal 0.

5. How does the inability for r to equal 0 affect our understanding of gravity?

The fact that r can never equal 0 in the equation F=G(Mm/r^2) is a fundamental aspect of our understanding of gravity. It means that objects must always have a distance between them in order for there to be a force of gravity acting between them. This helps us understand how gravity works and why objects in space follow certain orbits and trajectories.

Similar threads

Replies
2
Views
1K
Replies
1
Views
526
  • Classical Physics
Replies
10
Views
852
  • Classical Physics
Replies
5
Views
1K
  • Classical Physics
Replies
7
Views
745
Replies
5
Views
3K
Replies
1
Views
548
Replies
9
Views
1K
Replies
7
Views
1K
Back
Top