// Set's the rigidbody velocity to be 
// along the green axis of the transform
rigidbody.velocity = transform.up * 10;

using UnityEngine;
using System.Collections;

public class example : MonoBehaviour {
    void Example() {
        rigidbody.velocity = transform.up * 10;
    }
}

import UnityEngine
import System.Collections

class example(MonoBehaviour):

    def Example():
        rigidbody.velocity = (transform.up * 10)