CuboScript

using UnityEngine;
using System.Collections;

public class CubeScript : MonoBehaviour {

    private float randX, randY, randZ;
    private float randForceX, randForceY, randForceZ;

    private float maxForce = 250;
    private float minForce = -250;
    // Use this for initialization
    void Start () {

    }

    // Update is called once per frame
    void Update ()
    {
        if (gameObject.transform.position.y <= -8)
        {
            randX = Random.Range(-4.8f, 4.8f);
            randY = Random.Range(0.58f, 10f);
            randZ = Random.Range(-4.8f, 4.8f);
            gameObject.transform.position = new Vector3(randX, randY, randZ);
        }
    }

    void OnMouseDown()
    {
        randForceX = Random.Range(minForce, maxForce);
        randForceY = Random.Range(minForce, maxForce);
        randForceZ = Random.Range(minForce, maxForce);
        gameObject.rigidbody.AddForce(new Vector3(randForceX, randForceY, randForceZ));
    }
}