You have to keep in mind that [**Vibranium**][1] only absorbs kinetic energy ***directed at it***. If the shield absorbed ALL kinetic energy from any impact, it would be useless as a tool or weapon. Also, Vibranium does not absorb 100% of an impact's kinetic energy, only most of it.

When [Captain America][2] throws his shield at a person or object, keep in mind [Newton's First Law][3]:

> An object at rest stays at rest and **an object in motion stays in
> motion with the same speed and in the same direction unless acted upon
> by an unbalanced force**.

So what you have here is a near-invulnerable object travelling through the air at whatever speed it was thrown. Normally, the only thing that would stop such an object is the outside forces applied against it. In the case of the shield, however, most - but not all - of that outside force is nullified by the properties of the material.

Captain America has obviously learned how hard & fast to throw the shield in order to have it impact an object and still bounce back. In fact, his ability to accurately predict the trajectory of the shield is what makes him one of the few people in the Marvel universe who can wield the shield with any sort of effectiveness. In most people's hands, it would be no more effective than a big, near-invincible [Frisbee][4].

As for transferal of energy, it actually works the opposite of what you're thinking - the material prevents kinetic energy from being transferred through it, not out of it. For instance, when someone like [Thor][5] or [The Hulk][6] hits Captain America's shield, any other material would transfer that kinetic energy directly into the Captain's body. At the very least, his arm would be shattered, and after that his legs would probably turn into pulp. However, because of the Vibranium's properties most of that energy is negated, resulting in a much smaller impact as far as the Captain's bones & muscles are concerned.


  [1]: http://marvel.wikia.com/Vibranium
  [2]: http://marvel.wikia.com/Steven_Rogers_(Earth-616)
  [3]: http://www.physicsclassroom.com/class/newtlaws/Lesson-1/Newton-s-First-Law
  [4]: https://en.wikipedia.org/wiki/Flying_disc
  [5]: http://marvel.wikia.com/Thor_(Thor_Odinson)
  [6]: http://marvel.wikia.com/Robert_Bruce_Banner_(Earth-616)