If a coordinate system is rotating, that is time 't' is not independent, then does the acceleration transform as rank 1 tensor? I thought that it wouldn't because when time is changing, so acceleration will change in a more complicated way than a rank 1 tensor. Perhaps as a rank 2 tensor. This Q is really troubling me. There are two groups in my class, one saying it still transforms as a rank 1 tensor, the other saying it doesn't transform as a rank 1 tensor. Some even say that acceleration never transforms like a rank 1 tensor. I wonder how! I think it transforms like a rank 1 tensor if it goes fixed rotation, but 'rotating' coordinate system will mean that transformation is more complicated.