At a certain time, race car has only a northward accelearation with a magnitutde of a1 and at a later time delta-t, the same race car has only an acceleration a2, what is the magnitutde of its average "j" at this time? j= delta a/delta t I solved the q and got the correct answer, but when I looked at princeton's vector diagram, I was a little thrown off. Its a simple q asking to find the resultant change in acceleration I drew an arrow pointing north (+a1) and then another from the head of the arrow pointing north eastward (+a2) to find the resultant a Now, the explanation has an arrow eastward (+a2) and another from the head of the eastward arrow pointing south (-a1) I understand that there is no real difference between my and their vector diagram, but I'm a little weak at vectors, so want to be sure that my diagram was correct. Secondly, they said a2-a1(incorrect answer choice) will be correct if accelerations given were vector accelerations, it is not true for magnitude of the accelerations????