another inertial frame and we can only experimentally detect as to which frame is inertial and which frame is not (using Newton's first law). It should be noted that the more technical and deeper reason as to why Newtonian mechanics kind of needs absolute space, at a theoretical level, is to define inertial frames! Because all one can say otherwise is that an inertial frame moves at a constant velocity w.r.t. So, all one could actually observe was relative motion. this absolute space would both give the exact same outcome. the absolute space and an experiment that is done in an inertial frame moving at a constant velocity w.r.t. Thus, Newton's own theory predicts that an experiment that is done in the absolute rest frame, i.e., in the frame of reference that is at rest w.r.t. Why? Because all the equations of motion were invariant under Galilean transformation among inertial frames. It should be noted that the actual equations of Newtonian mechanics were such that one cannot do any experiment to detect as to whether an object is actually moving or at rest w.r.t. the frame of reference associated with this absolute space. He defined absolute motion as the motion that happens w.r.t. It just seems true that that is the reference frame with respect to which we ought to define true motion. We kind of associate the empty space we see in the pictures or imaginations of outer space as this absolute space in which all the motion of all the planets happens. This kind of immovable background of absolute space is very intuitive to all of us, I would presume. Absolute motion is the translation of a body from one absolute place into another: and relative motion, the translation from one relative place into another. Relative space is some movable dimension or measure of the absolute spaces which our senses determine by its position to bodies: and which is vulgarly taken for immovable space. "Absolute space, in its own nature, without regard to anything external, remains always similar and immovable. And that is exactly what happened in Newtonian mechanics. However! What if there were to be a uniquely preferred frame of reference? Well, in that case, it would make sense to say that we can define absolute motion as motion w.r.t. So, this is the basic definitional/conceptual sense in which all motion is trivially relative. This is obvious upon reflection because the only way to even speak of "change in position" is when you have a reference frame w.r.t. This is true both in Newtonian physics and in relativistic physics. Motion is defined as the phenomenon of an object changing its position over time with respect to a frame of reference. So, what kind of a concept is motion? Well, in an obvious and basic sense, motion is a manifestly relative concept. The Story of Relative and Absolute Motion In particular, they convey meaningful information only in relation to their units! For example, when I tell you that my bag weighs $20 \ \mathrm$ since the SI treaty. In a basic sense, all descriptions of quantities that have dimensionful units are necessarily relative.I will give a couple of examples, one of which has already been mentioned in other answers: There are various slightly different meanings and contexts in which the words relative or absolute might be used in physics but the basic impulse behind the idea remains the same. However, if I tell you that I have $32$ teeth then it is an absolute description of the cardinality of my teeth because it meaningfully defined in and of itself and does not need to refer to something else. In other words, to meaningfully know how many teeth I have, you need to refer to how many teeth my grandma has. Again, these are vectors so be sure to indicate both the magnitudes and directions when we put them into the equation.The Basic Meaning of Relative and AbsoluteĪ relative concept or a quantity is that which is defined in relation to something else - in such a way that a meaningful description of the concept or the quantity necessarily involves a reference to the something else in relation to which it has been defined.įor example, if I told you that I have twice as many teeth as my grandma has then I have given you a relative description of the cardinality of my teeth. If we use the appropriate set of equations for the type of motion in each step and plug in known quantities for angular velocities, angular accelerations, and rates or extension for each piece, we can add these pieces to our relative motion analysis equation from earlier.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |