Question

The driver of a car slams on the brakes when he sees a tree blocking the road. The car slows uniformly with an acceleration of -5.60 m/s^2 for 4.20 s, making mark straight skid marks of 62.4 m long ending at the tree. With what speed does the car then strike the tree?

Answer 1

average speed = 62.4 m / 4.20 s = (initial + final) / 2

change in speed = -5.60 m/s^2 * 4.20 s = initial - final

solve the system for final