Atrain starts from rest and accelerates uniformly until it has traveled 2.1 km and acquired a forward velocity of the train then moves at a constant velocity of for 400 s. the train then slows down uniformly at until it is brought to a halt. the distance traveled by the train while slowing down is closest to a train starts from rest and accelerates uniformly until it has traveled 2.1 km and acquired a forward velocity of the train then moves at a constant velocity of for 400 s. the train then slows down uniformly at until it is brought to a halt. the distance traveled by the train while slowing down is closest to 3.8 km. 4.2 km. 3.6 km. 4.4 km. 4.0 km.