Inertial adn non-inertial frames

  • Context: Undergrad 
  • Thread starter Thread starter jd12345
  • Start date Start date
  • Tags Tags
    Frames Inertial
Click For Summary

Discussion Overview

The discussion revolves around the concepts of inertial and non-inertial frames of reference, particularly in the context of a car that is accelerating. Participants explore how an observer within the car can determine whether they are in an inertial frame, despite the presence of forces acting on objects within that frame.

Discussion Character

  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • One participant suggests that a man in an accelerating car perceives an object at rest relative to himself, leading him to believe he is in an inertial frame and able to apply Newton's laws.
  • Another participant argues that the presence of a frictional force acting on the object indicates that the car is a non-inertial frame, as the object does not fall vertically when dropped.
  • A different viewpoint proposes that the man can determine if he is in a non-inertial frame by applying Newton's laws and comparing the results to experimental observations; discrepancies would indicate a non-inertial frame.
  • One participant challenges the notion of the car being inertial by stating that even if the car is not accelerating, the effects of gravity mean the observer is still in a non-inertial frame. They also suggest that hanging an object from the ceiling of the car can reveal horizontal acceleration if the object does not hang vertically.

Areas of Agreement / Disagreement

Participants express differing views on the conditions under which an observer can determine their frame of reference. There is no consensus on whether the car can be considered an inertial frame under the described conditions, and multiple competing perspectives remain present.

Contextual Notes

Some assumptions about the nature of forces and the definitions of inertial and non-inertial frames are not explicitly stated, which may affect the interpretations of the participants. The discussion does not resolve the mathematical implications of the forces involved.

jd12345
Messages
251
Reaction score
2
i know these topics are discussed many times and i have read many of them but still have a doubt.

Suppose a car is accelerating and there is an object and a man in the car. Object is ofcourse at rest with respect to man. The man does not know if the car is accelerating or not - he just sees the object at rest. So for him the car is inertial frame and he can apply Newtons laws there . How would he know if he is in an non-inertial frame?
 
Physics news on Phys.org
in car frame frictional force is acting on object ,still the object is at rest.so,it is obviously a non inertial frame.
for example, if he drops a ball it will not fall vertically downwards.
 
jd12345 said:
So for him the car is inertial frame and he can apply Newtons laws there . How would he know if he is in an non-inertial frame?
By applying Newtons laws and comparing to reality. If applying Newtons laws (using only interaction forces) doesn't match experiments, then he knows is in an non-inertial frame.
 
jd12345 said:
i
Suppose a car is accelerating and there is an object and a man in the car. Object is ofcourse at rest with respect to man. The man does not know if the car is accelerating or not - he just sees the object at rest. So for him the car is inertial frame and he can apply Newtons laws there . How would he know if he is in an non-inertial frame?


Hate to tell you this jd, but even if the car is NOT accelerating, he is still in a 'non-inertial' frame simply because his butt is pressing against the seat due to gravity.

In addition if the car is accelerating horizontally (down the street) as you have said,then he can easily tell simply by hanging the object on a string from the ceiling of the car. If the object does NOT hang vertically, then he and the car are accelerating horizontally.

...
 

Similar threads

  • · Replies 22 ·
Replies
22
Views
2K
  • · Replies 3 ·
Replies
3
Views
2K
  • · Replies 35 ·
2
Replies
35
Views
5K
  • · Replies 94 ·
4
Replies
94
Views
7K
  • · Replies 8 ·
Replies
8
Views
2K
  • · Replies 2 ·
Replies
2
Views
2K
  • · Replies 114 ·
4
Replies
114
Views
7K
  • · Replies 25 ·
Replies
25
Views
3K
  • · Replies 11 ·
Replies
11
Views
2K
  • · Replies 83 ·
3
Replies
83
Views
6K