I'd appreciate a tip here. A 10 kg object on a horizontal, unsmooth table is pushed to the right so as to have an intial velocity of 20 m/s. It comes to rest 5 seconds later, during which time its acceleration (deceleration?) was constant. I've already figured out the acceleration (4 m/s^2) and distance covered until coming to rest (50 m). However, I can't see how to get the kinetic friction force. Would the initial force (ma = 40 N) include the kinetic friction?