Identifying impending dangers through associations with things that have happened in the past is important for self-preservation.īut when our lives become dictated by thoughts and emotions attached to past events and potential future outcomes, standing peacefully rooted in the present becomes increasingly rare. Of course, it’s natural to spend moments of thought in the past or in daydreams of the future. Or, your thoughts are of the future: what will be, what could be, what might be, if… Your thoughts are of the past: what has been, what could have been, what you thought happened vs. Your mind is pulled into the past or the future, or both.
When you aren’t being present you become a victim of time. Secondly, just because two equations have the same format, that is a=b*c, does not mean that they are analogous.The easiest way to explain living in the present is to start by explaining what it means to not be present, since this is the state we have become habitually used to. In special circumstances, namely for homogeneous prismatic bodies, this value is related to the mass moment of inertia (units mass*length^2), but then you have to include density in the calculation, making it NOT purely "spatial". If you choose to define physical as "any aspect of an object or substance that can be measured or perceived without changing its identity" (as Wikipedia does, not that Wikipedia is right all the time, but I think this is a pretty fair definition) then clearly density, volume, second moment of area, moment of inertia, mass, modulus, and stiffness are all "physical" properties.įurthermore, in reply skeleton, the moment of inertia you refer to is not the moment of inertia we are discussing in this thread, but rather the second moment of area with units length^4. This conversation has transformed into a matter of semantics. Spatial and physical are not exclusive adjectives. These cross contributions are called the products of inertia. The direct contributions are called the moments of inertia. There are cross contributions or interactions from the other two axes, when we isolate any one of them. Vectors can be resolved into mutually exclusive contributions referred to each axes, called components. It is worth noting that these objects are more complicated than simple vectors. Where m is the mass of any particle and x,y is its perpendicular distance from the planes. (This is not the same as the second moment of area by the way.)Ģ)The product of inertia of a body about two planes which is defined as the sum taken over all particles of the body Where m is the mass of any particle and r is its distance from the axis. The moment of inertia of a body about an axis is defined as the sum taken over all particles of the body In this case the rotational inertia is simply \cos \alpha \cos \beta ġ)moments about the individual coordinate axis – these are called moments of inertia Yes indeed there is a physical significance.Ī simple dynamics treatment of rotational inertia sets the axis of rotation as one of the coordinate axis - x, y or z.
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