You can put this solution on YOUR website! Initial speed of ball=55mph---------------------speed of train
Final speed of ball=initial speed(55mph) + speed that it was pitched(55mph)=110mph for a brief period until it slows down.
Try dropping something eco-friendly out the window of a moving car and observe what it does. It will head out in the direction the car is traveling, bouncing along the highway, at the same speed of the car for a brief instance.
Hope this helps-----ptaylor