Is tilting your head back linear acceleraton? Super quick question

[scilearner]

Hello, I need to know what linear acceleration and angular acceleration of head is.

This is not for physics, this is what I'm thinking, if I'm wrong please correct me and tell my why not

 

Shaking head-angular acceleration

Tilting head back- angular acceleration (Just in case this becomes linear, why? angle is changing right?)

Nodding your head-angular accleration

Moving your head back and forth, in a straight line- linear acceleration

 

Thanks

Edited January 23, 2011 by scilearner

[swansont]

If the angle changes at a changing rate, it's angular. But even then, since the center-of-mass is changing speed, there are things you can do with linear acceleration, since the two are related by [math]\alpha = r\frac{d\omega}{dt}[/math]. There is also the centripetal acceleration, along r.

[scilearner]

If the angle changes at a changing rate, it's angular. But even then, since the center-of-mass is changing speed, there are things you can do with linear acceleration, since the two are related by [math]\alpha = r\frac{d\omega}{dt}[/math]. There is also the centripetal acceleration, along r.

 

Thanks for the reply swansont but I'm not a physics student. Could you please tell me if what I said above is right or wrong. I very much love to understand the physics concept though.

Edited January 23, 2011 by scilearner

[swansont]

I'm saying that you can look at angular acceleration as linear acceleration as well. It's not one or the other, because they are described by different coordinate systems.

[SMF]

Swansont, what is the coordinate system that deals with angular acceleration as linear? I read a fun piece a while back that talked about the use of centrifugal force as being appropriate for some engineering problems, but the coordinate system of a physicist observer looking at rotating objects from outside the system, would require that centrifugal force be fictive, while centripetal is not. Similarly, because atmospheric physicists are rotating within the earth coordinate system, Coriolis force is a useful concept, but a physicist observer outside the earth coordinate system would say it is fictive. Then along comes Einstein, and from his viewpoint, at least in terms of orbiting systems, gravitational force is fictive.

 

This is a slight divergence from the thread, but I find the notion of coordinate systems and their generalized everyday analog, “frames of reference,” is fascinating. SM

 

 

[swansont]

At any instant a point that has nonzero distance from the origin (of the rotation) will have a linear velocity. Underlying this point is that a Cartesian coordinate system is not orthogonal to a cylindrical or spherical one. It's not a matter of have either a linear vector or an angular one. To say that, you have to put yourself into a coordinate system where the components are orthogonal. You can have either rotational or radial motion, for example. But I can express rotational motion in terms of x and y.