title: Constant speed object in Box2D simulation
body: <p>I would like to make brick breaker like game but with bricks that react to physics.
  I set world to have 0 gravity and bricks have big linear and angular dumping set.</p>
  
  <p>But I have problem with ball. I would like my ball to have the same constant speed all the time. Even after colliding with bricks, walls and paddles (Yes, I have 2 of them). I know that this is not how physics work.</p>
  
  <p>But is there any way to make ball not loose speed on contact with some bodies? And make the ball bounce from bricks instantly without loosing it's energy but applying force to them (bricks)?</p>