B Inertial vs non inertial frames

  • B
  • Thread starter Thread starter rudransh verma
  • Start date Start date
  • Tags Tags
    Frames Inertial
AI Thread Summary
The discussion clarifies that whether a frame is inertial or non-inertial depends on the particle's acceleration rather than the frame itself. It highlights that Earth, while often treated as an inertial frame for practical experiments, is technically non-inertial due to its rotation. The effects of Earth's rotation can be negligible in certain contexts, such as in laboratory experiments, but are significant in fields like meteorology where the Coriolis force must be considered. The conversation emphasizes the importance of context in determining the appropriateness of treating a frame as inertial. Understanding these distinctions is crucial for accurate analysis in physics and engineering.
rudransh verma
Gold Member
Messages
1,067
Reaction score
96

I previously thought Earth is inertial frame and relative to Earth non accelerating frames are inertial too. But after watching this video, I came to know that it’s not the frame with respect to which we decide whether a frame is inertial or not. It’s the particle.
When a particle is not accelerating the frame is inertial. When it’s accelerating frame is non inertial.
But how the author is saying there is acceleration even when the net force is zero? I don’t get that part.
Also for example we take Earth and lift example. If our lift is accelerating then what does that make the earth, a non inertial frame or inertial ?
 
  • Like
Likes vcsharp2003
Physics news on Phys.org
rudransh verma said:
I previously thought Earth is inertial frame

It can't be since it is rotating. Rotating reference frames are not inertial. But sometimes we can neglect those effect, and treat frame connected with Earth as inertial, but that is an approximation.
 
  • Like
Likes vcsharp2003 and vanhees71
Another very illuminating movie, one of my favorites, is

 
  • Love
  • Like
Likes rudransh verma and Steve4Physics
rudransh verma said:
Also for example we take Earth and lift example. If our lift is accelerating then what does that make the earth, a non inertial frame or inertial ?
Part of the skill of physics/engineering is to know how to think about a problem.

Suppose you are doing experiments in a lab’ with colliding objects on an air-track. The fact that the Earth is rotating (so is non-inertial) is irrelevant – the effects on the experimental results are too small to have any detectable effects. You are therefore justified in treating the Earth as an inertial frame.

But if you are a meteorologist analysing large-scale patterns of air flow in the atmosphere., you cannot ignore the earth’s rotation. You must treat the Earth as a non-inertial frame. (Read about Coriolis force if you are not already familiar with it.)
 
  • Like
Likes rudransh verma and vanhees71
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...

Similar threads

Replies
94
Views
6K
Replies
18
Views
2K
Replies
5
Views
5K
Replies
15
Views
3K
Replies
13
Views
2K
Replies
2
Views
2K
Replies
7
Views
2K
Back
Top