title: How to move a few objects together to the left and still collide with ball?
body: <p>I got a few tower like things that a ball can jump on them.
  The problem is that I can't make the towers move like +5 to left and still be collided.
  Can someone help me?</p>
  
  <p><code>CODE</code></p>
  
  <pre><code>_G.mainGroup = display.newGroup()
  
  local rect=display.newRect( 200, 400, 100, 100 )
      physics.addBody(rect, "static", {density= 3,friction= 0.2})
      mainGroup:insert(rect)
  
  -- timer.performWithDelay(1, function(e)
      -- mainGroup.x = mainGroup.x - 4
      -- end, 0 ) 
  </code></pre>
  
  <p>I tried this in my code. and the rectangle moves without collison with a ball but it leaves behind a invisible replica which has collision becoz a ball is able to bounce on it. </p>