Driving home from school, you spot a ball rolling out into the street. You brake for 1.30s, slowing your 1000kg car from 17.0m/s to 10.0m/s. What was the average force exeerted on your car during braking?

F = ma = m(dv/dt) = 1000*(v_{f} - v_{i})/(t) = 1000 kg *(10.0 m/s - 17.0 m/s)/(1.30 s) = -5384.6 N