title: Can I scale a shape in box2d as sprite do?
body: <p>As we always use the function in cocos2d,I can scale my sprite whenever I want.Can I do the same thing in box2d?For example, I created a circle shaped body,then I want to make it bigger.</p>
  
  <p>I tried reassign the m_radius after I created a circle,but not work.</p>