When interacting with mobile devices, users have little patience for confusing interfaces or unnecessary steps that impede their progress. As designers, we must understand the role of momentum in effective user interface design and create experiences that keep our users moving forward.
Think about the act of checking email on a mobile device. This is probably one of our most efficient interactions with our phones; we do it while crossing the street, between conversations and even (for the dangerous few!) while driving. Every distracting bit of user interface (UI) that could get in the way of checking our email has been stripped from the design, making it a streamlined process that we love doing.