Inverse Square Law: What & How to Prove It

Click For Summary

Discussion Overview

The discussion revolves around the inverse square law, its definition, and methods of proving it. Participants explore its application in various forces such as electric, magnetic, and gravitational forces, as well as its geometric implications.

Discussion Character

  • Exploratory
  • Debate/contested
  • Technical explanation

Main Points Raised

  • Some participants define the inverse square law as stating that the force from a point source decreases with the square of the distance from the source, specifically as 1/r^2.
  • One participant suggests that the inverse square law can be demonstrated through geometric reasoning, particularly in relation to light intensity and area of a sphere.
  • Others challenge the validity of proving the inverse square law through human measurements, suggesting that empirical proof may not be reliable.
  • It is noted that not all forces conform to the inverse square law, which raises questions about its general applicability.
  • A participant argues that empirical methods, such as measuring the Coulombic force between charged objects, can demonstrate the inverse square relationship.

Areas of Agreement / Disagreement

Participants express differing views on the ability to prove the inverse square law, with some asserting it can be proven geometrically or empirically, while others question the reliability of human measurements and the law's applicability to all forces.

Contextual Notes

There are unresolved questions regarding the limitations of human measurements in proving the inverse square law and the conditions under which it applies to different forces.

eddybob123
Messages
177
Reaction score
0
What is the inverse square law and how do you prove it?
 
Physics news on Phys.org
eddybob123 said:
What is the inverse square law and how do you prove it?

That sounds interesting. What is it? Could you provide a web link or two to help us understand your question?

How do you think something like that could be "proved"? What is the formula for the area of a sphere maybe?
 
For forces like electric, magnetic, and gravitation, the inverse square law says that the force from a point source gets weaker the further you go from the source of the force. It falls off as 1/r^2 where r is the distance you are from the source. You prove it by measuring it. Other things obey the inverse square law too. If you have a light source, then the amount of light landing on a fixed area (like a piece of paper) facing the source will fall off as you move the area further away. It will fall off as 1/r^2. This is the geometric inverse square law. If you have a piece of paper at distance r, and you move it to 2r, you will have to make it 2 squared or four times larger in order for it to look the same size. This kind of inverse square law you can prove with geometry.
 
are you sure? because human measurements can't really prove it
 
Last edited by a moderator:
eddybob123 said:
are u sure? cause human measurements can't really prove it

Some forces do not obey the inverse square law, so for a general force, you can't prove it.

For the geometrical inverse square law, you can prove it, by geometry.
 
eddybob123 said:
are you sure? because human measurements can't really prove it

Course we can prove it empirically. We take two pith balls and give them each a net charge and then measure the Coulombic force as a function of distance. We will see that the force drops off as 1/r^2 with some proportional constant.
 

Similar threads

Undergrad Electricity and Magnetism: Verifying the Inverse Square Law
  • · Replies 3 ·
Replies
3
Views
2K
High School Who Created the Inverse Square Law Theory
  • · Replies 3 ·
Replies
3
Views
4K
High School Why are 2/3 of my brake lights required to work by law?
  • · Replies 11 ·
Replies
11
Views
2K
High School Proof of inverse square law for gravitation?
  • · Replies 18 ·
Replies
18
Views
3K
Undergrad Sound pressure and inverse distance law
  • · Replies 5 ·
Replies
5
Views
3K
Undergrad Physical approximation to inverse square law using magnet(s)
  • · Replies 12 ·
Replies
12
Views
2K
Undergrad How inverse square law is derived from area of sphere
  • · Replies 12 ·
Replies
12
Views
4K
Undergrad Field Strength of Permanent Magnets -- Inverse square or inverse cube?
  • · Replies 9 ·
Replies
9
Views
2K
Undergrad Inverse Square Law for Black Holes
  • · Replies 32 ·
2
Replies
32
Views
3K
High School History of the term "square-cube law?"
  • · Replies 8 ·
Replies
8
Views
5K