title: Trying to get my head around simulating momentum / inertia witih a UIRotationGestureController
body: <p>Okay, so I'm trying to make a 'Wheel of Fortune' type of effect with a wheel shape in iOS, where I can grab and spin a wheel. I can currently drag and spin the wheel around to my heart's content, but upon releasing my finger, it stops dead. I need to apply some momentum or inertia to it, to simulate the wheel spinning down naturally.</p>
  
  <p>I've got the velocity calculation in place, so when I lift my finger up I <code>NSLog</code> out a velocity (between a minimum of 1 and a maximum of 100), which ranges from anywhere between 1 and over 1800 (at my hardest flick!), now I'm just trying to establish how I would go about converting that velocity into an actual rotation to apply to the object, and how I'd go about slowing it down over time.</p>
  
  <p>My initial thoughts were something like: begin rotating full circles on a loop at the same speed as the velocity that was given, then on each subsequent rotation, slow the speed by some small percentage. This should give the effect that a harder spin goes faster and takes longer to slow down.</p>
  
  <p>I'm no mathematician, so my approach may be wrong, but if anybody has any tips on how I could get this to work, at least in a basic state, I'd be really grateful. There's a really helpful answer here: <a href="https://stackoverflow.com/questions/9624804/iphone-add-inertia-momentum-physics-to-animate-wheel-of-fortune-like-rotating">iPhone add inertia/momentum physics to animate &quot;wheel of fortune&quot; like rotating control</a>, but it's more theoretical and lacking in practical information on how exactly to apply the calculated velocity to the object, etc. I'm thinking I'll need some animation help here, too.</p>
  
  <p>EDIT: I'm also going to need to work out if they were dragging the wheel clockwise or anti-clockwise.</p>
  
  <p>Many thanks!</p>