Question 1. A test of the prototype of a new autombile shows that the minumin distance for a controlled stop from 91km/h to zero is 47m. Find the acceleration. The acceleration due to gravity is 9.81m/s^2. I tried using kinematic equations, transforming km/h to m/s. I plugged in the velocity, change in positon and found the time to plug into my kinematic eqaution but my answer of -6.97 was wrong

Question 2. A speeder traveling at a constant speed of 85km/h races past a billboard. A patrol car pursues from rest with constant acceleration of 5(km/h)/s until it reaches its maximum speed of 128km/h which it maintains until it catchez the speeder

I have no idea how to solve this one Please help