title: Ball line collision
body: <p>In my Android game I detected the collision of a ball and line, but I don't know how to change ball velocity in relation with line angle.</p>
  
  <pre><code>if(ball.collidesWith(line)){
      ball.nextTile();
      ball.mPhysicsHandler.setAngularVelocity(65);
      float xvelo=ball.mPhysicsHandler.getVelocityX();
      float yvelo=ball.mPhysicsHandler.getVelocityY();
      double lineAngle = Math.atan2(line.getY2() - line.getY1(), 
                                    line.getX1() - line.getX2()) * 180 / Math.PI;
  
      ???????????????????????????????
  
  }
  </code></pre>