What is inertia? What is its source?

  • Thread starter Thread starter SinghRP
  • Start date Start date
  • Tags Tags
    Inertia Source
AI Thread Summary
Inertia is defined as the resistance of an object to changes in its state of motion, often linked to mass. The term is ambiguous and can refer to various concepts like mass, momentum, or energy required for acceleration. Historical figures like Galileo, Newton, and Einstein have contributed to the understanding of inertia, with Einstein proposing that inertial mass and gravitational mass are equivalent. Mach's hypothesis suggests that inertia may arise from the mass of the universe, though this remains unproven. The discussion emphasizes the need for clarity in defining inertia and its implications in physics.
SinghRP
Messages
73
Reaction score
0
What is inertia? What is its source? Is inertial mass mass? Do gravitational mass and inertial mass have the same sign?
 
Physics news on Phys.org


Inertia is a term physicists don't use by itself all that often. The meaning of "inertia" is a bit ambiguous: Does it mean mass, linear momentum, angular momentum, mass*distance squared, or something else? Without context, it is a bit difficult to tell. What do you mean by "inertia"?

Physicists eschew the word for a simple reason: Why use an ambiguous term when there are perfectly good and much less ambiguous alternatives?
 


Well, I started this inertia topic. This one is not clear even today. I am working on it as a research topic.
Galileo, Eotovos, Newton, Mach, Enistein, Dicke addressed it. Inertia is resistance to acceleration. Mach thought, but could not prove it, that inertia is due to the rest of the mass in the universe. Einstein's principle of equivalence: inertial mass and gravitational mass are the measures of the same quantity. General Relativity has not yet accommodated it.
Well, maybe some one can shed some light.
 


Inertia: the resistance an object has to a change in its state of motion.
 


Are you familiar with what heat capacity is? Its the amount of energy it takes to raise the temperature of something by 1 degree.

Inertia would be quantitatively analysed as the amount of energy it takes to raise the speed of a mass by 1m/s . Something quite heavy would have a large value for inertia, just like water has a large value for heat capacity.

Also note that this works the other way around. It would take the same energy to slow it down as it would to speed up, and the same energy to heat up as it would to cool down.
 


Hamden and DH,

I agree with you. Inertia is not only with mechanical motion. One example is the one, DH, you cited.

In the mechanical world, I like to use momentum (including angular moentum) instead of motion, even though motion is by all means okay. Reason: orbital, vibrational and spin motions may not be included in motion when describing inertia. (At very low tepperatures you will need more heat to raise the temperature by 1 degree.)

Einstein: gravitational mass is numerically equal to inertial mass. Scenario: a body falling to the earth. As the gravitational mass is more, gravitational force increases; but then inertial mass is equally more, which increases the inertia or resistance. That's why two bodies with different masses fall with the same acceleration.

Let's continue this discussion. What's the source of inertia? Mach thought it was due to the rest of the universe. [The body does not resist, but the universe does?] What do you think?
 

Thread 'Is calling fictitious forces "not real" just about terminology?'

Hi there, im studying nanoscience at the university in Basel. Today I looked at the topic of intertial and non-inertial reference frames and the existence of fictitious forces. I understand that you call forces real in physics if they appear in interplay. Meaning that a force is real when there is the "actio" partner to the "reactio" partner. If this condition is not satisfied the force is not real. I also understand that if you specifically look at non-inertial reference frames you can...
View full post »

Thread 'Derivation of Hamilton's Principle: Questions'

I have recently been really interested in the derivation of Hamiltons Principle. On my research I found that with the term ##m \cdot \frac{d}{dt} (\frac{dr}{dt} \cdot \delta r) = 0## (1) one may derivate ##\delta \int (T - V) dt = 0## (2). The derivation itself I understood quiet good, but what I don't understand is where the equation (1) came from, because in my research it was just given and not derived from anywhere. Does anybody know where (1) comes from or why from it the...
View full post »

Similar threads

I Calculating Mass Inertia Product - Examples 1 & 2
Replies
2
Views
2K
Why does mass/energy have inertia?
Replies
22
Views
3K
I Explanation of parallel axis theorem
Replies
2
Views
1K
I Moment of inertia of human body with limbs at an angle
Replies
12
Views
2K
Law of inertia (inertial observer and inertial frames of reference)
Replies
2
Views
1K
Moment of inertia where mass and torque are at a different positions
2
Replies
69
Views
5K
I Effects of External Torques on the Angular Momentum of Asymmetric Bodies
Replies
3
Views
2K
I Counter-rotating mass to counteract inertial spin
Replies
10
Views
2K
What is the source of inertia?
Replies
2
Views
1K
I Resolve moment of inertia at an angle
Replies
2
Views
2K

Hot Threads

Recent Insights

Back
Top