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

In summary, the conversation discusses the equation dr/dt = w(t)xr(t) in the context of a motion around a fixed axis, where r(t) is the position and w(t) is the angular velocity. The question is whether this equation remains true if the axis vector, D, is not constant but dependent on time. The answer is unclear and further assistance may be needed.
  • #1
yetar
54
0
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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  • #2
dr/dr = w(t)xr(t).
Do you mean dr/dt ? I'm not clear about the description.
 
  • #3
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 dependant 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 dependant of the time t?
Is it still true that dr/dt = wxr?
Where w is the angular velocity.
 
  • #4
Yetar, I'm sorry I can't answer your question. Maybe someone else can help.
 

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

1. What is "motion about a moving axis"?

Motion about a moving axis refers to the movement of an object or system in which the axis of rotation or motion is itself moving. This can occur in various scenarios, such as a spinning top on a moving train or a rotating planet orbiting a moving star.

2. How does an object move when its axis is moving?

The movement of an object when its axis is moving depends on the direction and speed of the axis. If the axis is moving in a straight line, the object will also move in a straight line with the same speed. If the axis is rotating, the object will also rotate around the moving axis.

3. What causes motion about a moving axis?

Motion about a moving axis can be caused by various factors, such as external forces acting on the system, the properties of the object or system itself, or the relative motion of the reference frame in which the motion is observed.

4. What are some real-life examples of motion about a moving axis?

One example of motion about a moving axis is the movement of a spinning top on a moving surface, such as a train or a spinning plate on a stick that is being moved. Another example is the rotation of a planet around a moving star, such as the Earth orbiting the Sun.

5. How is motion about a moving axis different from motion about a fixed axis?

Motion about a moving axis is different from motion about a fixed axis in that the axis of rotation or motion itself is moving in the former, while it remains stationary in the latter. This can result in different patterns and changes in the movement of the object or system.

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