Discussion on Laws of Motion

here is a tip for solving moving car related question
When friction is the only net force acting on a decelerating body (e.g., bike/boy, block of wood, car), the mass of the body is immaterial. m cancels out, leaving the accelerating (deceleration) a = kg; where k is the coefficient of friction sliding or rolling, makes no difference. Also, notice what happens on a slippery road, when k goes down. The car's deceleration goes down with the k, which is why we leave more room between us and the car in front when the road is wet and slippery.