The driver of a truck slams on the brakes when he sees a tree blocking the road. The truck slows down uniformly with acceleration −5.80 m/s2 for 4.20 s, making skid marks 57.2 m long that end at the tree. With what speed does the truck then strike the tree?

Question

Vi=Vf-at
Vi=2xt-Vf

Vf-at=2xt-Vf
Vf-(-5.8 x 4.20) = 2(57.2 x 4.2)-Vf
Solve for final velocity = 228.06 but that answer is incorrect.