Where is the intertial frame of reference applicable?

[readingforev]

(Please forgive me for the obvious stupidity of this question)

I'm trying to understand Newton's laws down to the last detail, because that is how I study things. However, where would the principle of inertia ever take place? And since Newton's laws are only applicable in an inertia frame reference, are the laws correct? How would an object in motion going at its constant velocity without any "forces" get in motion in a frame of inertia without an initial force? Does it mean that it was in a place that started it's one initial push of force then it entered a place with no forces, where it would continue on forever?

Thank you for any answers in advance.

 

[Chestermiller]

Welcome to Physics Forums.

The inertial frame of reference refers to that of the observer, not to the object. It is the observer who has no forces acting on him. He can use his inertial frame of reference coordinate system to quantify the kinematics of the object's motion, and to apply Newton's laws. Another observer from another inertial frame of reference can do the same, and still have Newton's laws properly apply in his frame of reference. This is how the principle of inertia works.

 

[readingforev]

Where would an observer have no forces acting upon him? How is it used to quantify the kinematics?

Thank you for your patience.

 

[Chestermiller]

Let's start over. Check out the following PF thread: https://www.physicsforums.com/showthread.php?t=10952

 

[Nickie]

The concept of an inertial frame of reference is a fundamental part of Newton's laws of motion. An inertial frame of reference is a frame in which Newton's first law holds true - an object in motion will continue to move at a constant velocity unless acted upon by an external force. This means that in an inertial frame of reference, there are no forces acting on the object to change its state of motion. This frame can be thought of as a reference point for measuring the motion of objects.

Inertial frames of reference can be found in many different situations. For example, a stationary observer on the ground can be considered to be in an inertial frame of reference, as there are no external forces acting on them to change their state of motion. Similarly, an object moving at a constant velocity in outer space can also be considered to be in an inertial frame of reference, as there are no external forces acting on it.

It is important to note that an inertial frame of reference is a theoretical concept and does not exist in the physical world. In reality, there are always external forces acting on objects, even if they may be very small or difficult to detect. This is why Newton's laws are considered to be idealized models that may not perfectly match real-world situations.

Regarding your question about an object in motion without any forces, it is important to remember that an object's initial state of motion is determined by the forces acting on it at that moment. In an inertial frame of reference, if there are no external forces acting on the object, it will continue to move at a constant velocity. However, this does not mean that there were no forces acting on it at all, but rather that there were no external forces acting on it in that particular frame of reference.

In conclusion, the concept of an inertial frame of reference is applicable in many situations and is a crucial part of understanding Newton's laws of motion. While it may seem like a theoretical concept, it helps us to better understand the motion of objects and make predictions about their behavior. I hope this helps to clarify your understanding of this topic.