Ahh yes, I suppose constant magnitude would be an accurate term. Just re-reading through the question (and without looking at the picture obviously), I can't see the point. There is always going be tangental acceleration, and there also must always be normal acceleration, although this will change.siddharth said:Is it? The direction of [tex] e_\phi [/tex] continously changes with [itex] \phi [/itex]. So, even if the speed is the same, the direction of velocity changes, doesn't it? So how can the tangential acceleration (ie, acceleration along [tex] e_\phi [/tex]) be the same?