Inertial reference frames.

In summary, an inertial frame of reference is one in which there is no acceleration. If there is a constant speed with a non-constant velocity, this implies acceleration and the frame is no longer inertial. An object on a rotating turntable will not stay in place but will accelerate away from the observer. The apparent forces experienced by objects in an accelerating plane depends on their mass, but even a massive object will still experience an inertial force and move backwards.
  • #1
Jadenag
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An inertial frame is one which is not accelerating.
i.e if I'm sitting in an accelerating bus or plane I'm not an inertial observer however if I am in a bus or train traveling at a constant velocity i.e zero acceleration then I am an inertial observer.

One thing Id like to ask here is that if I have a constant speed but a non constant velocity that means I have a non constant acceleration. So that means I'm no longer an inertial observer correct?

However If I stand on a turn table rotating at a constant speed.
And if I place an object on the turn table with me. Then won't that object stay there? Or would that then depend on the mass of the object and the angular velocity of the turn table? In my opinion I would not be an inertial observer.


One last thing I was going through Dr shankars( I believe) lecture of Yale on CM. And he used the example where he said that when you place an object on an accelerating plane it travels back. And that an object at rest did not remain at rest hence justifying that that is not an inertial frame. But doesn't the moving of the object backwards depend on its mass/inertia? Its not absolutely necessary for an object to move back right? Whats if its too heavy ie massive.

- Thankyou, Jade
 
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  • #2
Jadenag said:
An inertial frame is one which is not accelerating.
i.e if I'm sitting in an accelerating bus or plane I'm not an inertial observer however if I am in a bus or train traveling at a constant velocity i.e zero acceleration then I am an inertial observer.

One thing Id like to ask here is that if I have a constant speed but a non constant velocity that means I have a non constant acceleration. So that means I'm no longer an inertial observer correct?

Yes. A non-constant velocity means that you are experiencing acceleration. Acceleration implies non-inertial frame of reference.
However If I stand on a turn table rotating at a constant speed.
And if I place an object on the turn table with me. Then won't that object stay there?
Nope. It'll accelerate away from you (unless friction or some other force retards it). It will follow the dictates of the inertial forces that it feels in that frame of reference.
Or would that then depend on the mass of the object and the angular velocity of the turn table? In my opinion I would not be an inertial observer.
From your point of view standing on the turntable, the forces that an object appears to experience will of course depend upon the angular velocity of the turntable.
One last thing I was going through Dr shankars( I believe) lecture of Yale on CM. And he used the example where he said that when you place an object on an accelerating plane it travels back. And that an object at rest did not remain at rest hence justifying that that is not an inertial frame. But doesn't the moving of the object backwards depend on its mass/inertia? Its not absolutely necessary for an object to move back right? Whats if its too heavy ie massive.
The heavier the mass, the larger the apparent inertial force. Making the mass larger does not change the outcome, in fact it makes it more certain! if the plane accelerates, it will leave anything not bolted down, or held in place by friction, behind. Remember, in reality it is the plane that is accelerating and the other objects that just want to stay as they are (Newton's 1st law!).
 

What is an inertial reference frame?

An inertial reference frame is a coordinate system in which Newton's laws of motion hold true, and objects at rest will remain at rest unless acted upon by an external force. It is a frame of reference that is not accelerating or rotating.

How is an inertial reference frame used in science?

Inertial reference frames are used in science to study the motion of objects and to make accurate measurements. They provide a consistent and reliable frame of reference for analyzing the behavior of physical systems.

What is the difference between an inertial and non-inertial reference frame?

An inertial reference frame is one that is not accelerating or rotating, while a non-inertial reference frame is one that is accelerating or rotating. In an inertial frame, Newton's laws of motion hold true, while in a non-inertial frame, additional forces must be considered.

How do you determine if a reference frame is inertial?

A reference frame can be considered inertial if an object at rest in that frame remains at rest and an object in motion maintains a constant velocity without any external forces acting upon it. This can be tested through experiments and observations.

What are some examples of inertial reference frames?

An example of an inertial reference frame is a room on a stationary train. As long as the train is not accelerating or decelerating, the objects within the room will behave in accordance with Newton's laws of motion. Other examples include a spaceship moving at a constant velocity in outer space or a car traveling at a constant speed on a straight road.

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