A 5000-kg car moving at 4 mile/hour collides and couples with an 8000kg car, which was initially at rest. The common final speed of these two cars in (mile/hour) is: 1.54 4 2.5 1.31 1 A 3.0-kg object moving in the positive x direction has a one-dimensional elastic collision with a 5.0kg object initially at rest. After the collision the 5.0kg object has a velocity of 6.0m/s in the positive x direction. What was the initial speed of the 3.0kg object? 6.0m/s 5.5m/s 7.0m/s 8.0m/s 4.5m/s