Recent content by tahsphere

In biology, it's not usual to work with this kind of data. I don't have experience of a physicist or a mathematician and my supervisor don't give me reference. I read the notes but I have difficulties to find a direct application for my problem. A priori, I have no information about radius of...

Hello, Any solution ? Maybe I don't give good explanations. If a sphere is spinning around an axis with its center staying fixed, how can I know its angular velocity from points at its surface recorded each minutes ? For example, the sphere below is rotating around (0, 0, 1) with an...

Hello, It's not really a homework, it's just a part of my project in biology for my master thesis. I want to know the rotation speed of a sphere (angle/min). Using magnetic field, I recorded points on the surface of the sphere every minute (figure above). I want that this angle do not depend...

Hello, I wanted to find a better way to estimate axis of rotation. I found the Kabsch algorithm for calculating the optimal rotation matrix that minimizes the RMSD from 3 points or more. Thus, I have my rotation matrix R, I can deduct the axis of rotation with the eigen vector...

I don't know how to do that. I just know that the angle between 2 points A (xA,yA,zA) and B (xB,yB,zB) through the center of the sphere is \theta = \arccos (xA xB + yA yB + zA zB). I use projections onto the plane passing through the plane and then calculate theta for each time t.

Hello, thank you for your answers. I understand now what the linear speed is. Yes, the center of my sphere stay centered at the origin. If I have theses points Pi : longitude : P1=pi/4; P2=2*(pi/4); P3=3*(pi/4); P4=pi; P5=5*(pi/4); P6=6*(pi/4); P7=7*(pi/4) colatitude : Pi=0.05 radians...

I am not physicist but biologist, I am not sure to use the good words. I don't think that my linear speed is zero. For example, my points can be on a small circle with one revolution each 6 hours or more. I want to calculate the speed so that, for example, one turn on a sphere parallel is 360°...

Homework Statement Hello everyone. Each minute, I have 3d coordinates of points at the surface of a unit sphere (with center at (0;0;0)) rotating with an axis which can (slightely?) change over time. I want to know the linear speed (s) of this sphere. I don't know how to find r at each time...