// Moves the rigidbody forward
constantForce.relativeForce = Vector3.forward * 10;

using UnityEngine;
using System.Collections;

public class example : MonoBehaviour {
    void Example() {
        constantForce.relativeForce = Vector3.forward * 10;
    }
}

import UnityEngine
import System.Collections

class example(MonoBehaviour):

    def Example():
        constantForce.relativeForce = (Vector3.forward * 10)