title: How to make a b2body move at a constant speed with box2d
body: <p>I am making a box2d game and have enemies fly in from the left side of the screen to the right side of the screen. If I apply a force in the tick method like shown below, the enemies increasingly move faster over time. I want the enemies to move at a constant pace instead of increasing their speed. How can I do this. I have tried impulses and forces, but they don't seem to keep a constant speed</p>
  
  <pre><code>b2Vec2 forceA = b2Vec2(15, -b-&gt;GetMass() * world-&gt;GetGravity().y);
  b-&gt;ApplyForce(forceA, b-&gt;GetWorldCenter() );
  </code></pre>