Two trains are headed toward each other on the same track with equal speeds of 20m/s. When they are 2 km apart, they see each other and begin to decelerate. A.) If their accelerations are uniform and equal, what must their acceleration be in order to barely avoid a collision? b.) if only one car slows down with this acceleration (the other continuing with its original speed), how far will the decelerating train travel before it collides with he other train?