Does the equation dr/dr = w(t)xr(t) hold true for a changing axis vector?

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Homework Help Overview

The discussion revolves around the equation dr/dr = w(t)xr(t) in the context of motion about a fixed axis, specifically questioning its validity when the axis vector changes over time.

Discussion Character

  • Conceptual clarification, Assumption checking

Approaches and Questions Raised

  • Participants explore the meaning of the equation and its components, with some questioning whether dr/dr should be interpreted as dr/dt. Others discuss the implications of a changing axis vector D(t) on the validity of the equation.

Discussion Status

The discussion is ongoing, with participants seeking clarification on the equation and its terms. Some have provided insights into the definitions of the vectors involved, while others express uncertainty about the implications of a non-constant axis vector.

Contextual Notes

There is a mention of specific variables such as r0, R, and h0, as well as the nature of the vectors involved, which may influence the interpretation of the equation. The original poster's question highlights the complexity introduced by a changing axis vector.

yetar
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In a motion about a fixed axis, where the position is r(t) and the angular velocity is w(t), we know that dr/dr = w(t)xr(t).
My question, does this equation remains true if the axis vector is changing by the time t? Why so?
Thank you.
 
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dr/dr = w(t)xr(t).
Do you mean dr/dt ? I'm not clear about the description.
 
Mentz114 said:
Do you mean dr/dt ? I'm not clear about the description.

Yes, dr/dt.
r(t) = r0*R+h0*D
Where r0 is a constant distance scalar, and h0 is the distance from the plane that D is normal to.
D is a unit vector, the axis of rotation, so the particle rotates around the axis D. And R is a unit vector, which is the radial vector. R is the opposite direction of the centerpital accelaration.
R is dependent of t, the time.
On a motion around a fixed axis, D is a constant vector, and in this case:
dr/dt = r0*dR/dt = wxr
My question is, what happens when D is not a constant, but instead D(t) is a vector dependent of the time t?
Is it still true that dr/dt = wxr?
Where w is the angular velocity.
 
Yetar, I'm sorry I can't answer your question. Maybe someone else can help.
 

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