Please find attached a schematic showing the relationship between the 4 main components of a automotive driveline. I do not understand the reason for the directions of the torques and angular velocities in the schematic. At first, I thought this had something to do with equations and unknowns, but this would not be possible since every variable in there is inter-related. Could it be that the arrows pointing to left imply "load" and the arrows pointing to the right imply "power" ? I am not quite sure how to understand this. (Schematic taken from the book Vehicle dynamics by Rajesh Rajamani,chapter 4).