I can see a few things from your code:

1) Set gravity outside of action. It should be set once and not have to rely on entity creation (and it's action) to do it.

2) you have damping set at 90... this means your objects will be so damped, they won't move unless you apply a force EVERY frame. Drop that value a bit.

3) We have no idea how you apply the force. This is a big part of the problem and solution.

Don't know that the above will solve the problem, but it's all I can see that might be wrong from what you posted.