I have an answer to this question and then a question: A car with a mass of 1,000kg moves at 20 m/s. What is the braking force needed to bring the car to a halt in 10s. I used m2v2-m1v1 and came up with -20,000 kg(m/s) then -20,000kg(m/s)/10s I came up with -2,000 N Is this right? Does the negative mean slowing down? Am I even on the right path?