You are traveling down the street at 9.0 m/s when a dog runs out in from the car. If you apply the brakes immediately, resulting in a uniform acceleration of 4.1 m/s(squared), how long does it take you to stop and how far away must the dog be to avoid getting hit?

If you accelerate you are more likely to hit the dog than avoid him. Did you mean decelerate?

Or perhaps, the OP missed a negative sign in front of the value.

Anyway, the equation v^2 = u^2 + 2as is used for the first part, and for the second part, v = u + at is used.