GenCubeExplode.cs

using System.Collections;
using System.Collections.Generic;
using UnityEngine;

public class GenCubeExplode : MonoBehaviour
{
    public float radius = 1.0F;//Radius of explosion becareful how far apart you set object they can be caught in this explosion
    public float power = 10.0F;//power applied to objects hit

    void Start()
    {
        Vector3 explosionPos = this.transform.position;//inital position of explosion
        Collider[] colliders = Physics.OverlapSphere(explosionPos, radius);//create imaginary sphere to detect what was hit by explosion
        foreach (Collider genCube in colliders)
        {
            if(genCube.tag == "genCube")//if its a genCube apply force and turn on gravity for object
            {
                Rigidbody rb = genCube.GetComponent<Rigidbody>();

                if (rb != null)
                {
                    rb.AddExplosionForce(power, explosionPos, radius, 3.0F);
                    rb.useGravity = true;
                }     
            }
        }
    }
}