public float pushForce = 10f; // сила толчка
private bool canPush = false; // можно ли толкать объект

private Rigidbody rigidbody;

private void Awake(){
    rigidbody = GetComponent<Rigidbody>();
}

private void OnCollisionStay(Collision collision)
{
    if (collision.gameObject.CompareTag("Player"))
    {
        canPush = PlayerTransform.FormEarth.activeInHierarchy;
    }
}

private void OnCollisionExit(Collision collision)
{
    if (collision.gameObject.CompareTag("Player"))
    {
        canPush = false;
    }
}

private void FixedUpdate()
{
    if (canPush)
    {
        rigidbody.AddForce(transform.forward * pushForce, ForceMode.Impulse);
    }
}

public GameObject[] gameObjects;
private int counter = 0;

void Update(){
    SelectedTest();
}

public void SelectedTest(){
    if (Input.GetKey(KeyCode.K)){
        for(var i = 0; i < gameObjects.Length; i++){
         gameObjects[i].SetActive(i == counter);
        }

        counter = counter >= gameObjects.Length - 1 : 0 : counter + 1;
    }
}

[spoiler][img]http://s1.uploadpics.ru/images/byAbiXBuUU.jpg[/img][/spoiler]