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If so.. is it safe to say the opposite: that any object in a state of equilibrium is in an inertial reference frame?

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- Thread starter runner108
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If so.. is it safe to say the opposite: that any object in a state of equilibrium is in an inertial reference frame?

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Vanadium 50

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Also, by "equilibrium" I assume you mean the usual definition used in statics: the sum of all forces is 0 and the sum of all torques is 0.Is it safe to say that any objectat restin an inertial reference frame is at a state of equilibrium?

If so.. is it safe to say the opposite: that any object in a state of equilibrium isat restin an inertial reference frame?

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I would say yes with the following clarification in bold. Also, by "equilibrium" I assume you mean the usual definition used in statics: the sum of all forces is 0 and the sum of all torques is 0.

That is what I meant, and thank you for your insight.

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If we say that acceleration is absolute and that an object on its geodesic undergoes no proper acceleration, isn't that the object that in all reference frames should be considered to be not accelerating of the three? It seems, however to be the one at rest.

All three are in states of equilibrium and will require some force to deviate from their paths.

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A.T.

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You still confuse proper acceleration and coordinate acceleration. Always specify which one you mean, instead just saying "acceleration/accelerating".If we say thataccelerationis absolute and that an object on its geodesic undergoes no proper acceleration, isn't that the object that in all reference frames should be considered to be notacceleratingof the three? It seems, however to be the one at rest.

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For example, consider an accelerometer on the edge of a rotating disk in deep space. The accelerometer measures the centripetal acceleration. Considered from an inertial frame this accelerometer reading matches the second time derivative of its coordinates, so the coordinate acceleration and the proper acceleration are equal. However, now consider the disk's rotating reference frame. In this frame the second time derivative of its coordinates is zero, so the coordinate acceleration does not match the measured proper acceleration. To explain this we include a fictitious force, the centrifugal force, which counteracts the centripetal force. Such fictitious forces, being fictitious, are not measurable by accelerometers. Both frames agree on the proper acceleration (the measured acceleration in each case), but they disagree about the coordinate acceleration (equal to the measured acceleration for the inertial frame, equal to 0 for the rotating frame).

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DaleSpam: Are you a teacher? Very impressive. Thank you. You eased a troubled mind.

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