This is Dr.Bob and he is a scientist and he loves to teach and learn new things.
Dr.Bob is trying to figure out how when the baseball hits the bat the ball goes flying and changes direction but the bat does not.
This happen's because of Newton's second law. Newton's second law states that a force applied to an object will cause that object to accelerate, or change its speed or direction. The baseball bat applied a force to the ball, which changed the ball's speed and direction.
Now that Dr.Bob has his information he goes and writes it down so he remembers.
Now that Dr.Bob knows about Newton's second law he wants to learn about Newton's first law and he chooses to learn about it with hockey.
If you slide a hockey puck on ice, eventually it will stop, because of friction on the ice. It will also stop if it hits something like a player's stick or a goalpost. Dr.Bob says this is Newton's first law because an object at rest will stay at rest. He also said it has to deal with inertia which is correct as well.