Physical collisions use Collision.

void OnCollisionEnter(Collision collision)
{
    Debug.Log(collision.gameObject.name);
}

void OnCollisionStay(Collision collision)
{
}

void OnCollisionExit(Collision collision)
{
}

Contact data:

ContactPoint contact =
    collision.GetContact(0);

Vector3 point = contact.point;
Vector3 normal = contact.normal;

Impact strength:

float impact =
    collision.relativeVelocity.magnitude;