Unity3d Arkanoid platform collision problem

Hello dear friend!
I have a working code, but it doesn’t work as it should for the platform.

velocity = Vector3.Reflect(velocity, collision.contacts[0].normal);

How to implement this idea?
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private void OnCollisionEnter(Collision collision)
{
    Debug.Log(collision.contacts[0].point.z);
}

This function returns the platform’s position, not the point of contact.

Thanks in advance, I hope you understand me.

http://answers.unity.com/comments/1738989/view.html

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