How do I find velocity from acceleration?? 1. An automobile and a truck start from rest at the same instant, with the automobile initially at some distance behind the truck. The truck has a constant acceleration of 2.00 , and the automobile an acceleration of 3.42 . The automobile overtakes the truck after the truck has moved a distance 41.0 . r=r+Vt+1/2at^2 I get 40=vf^2/4, which gives me 40, but that's not right.