Make a virtual sphere jump

I'm trying to make a sphere jump over a target, but the sphere goes forward camera when I press space (doesn't up), and the sphere doesn't goes down. I'm using vuforia 5 extension and unity 5

my code

using UnityEngine;
using System.Collections;

public class Jump : MonoBehaviour {
public Rigidbody sphera;
public float jump;

// Use this for initialization
void Start () {
sphera = GetComponent<Rigidbody>();
}

void Update () {
Vector3 movement = new Vector3(0, jump, 0);
if (Input.GetKeyDown (KeyCode.Space )){
sphera.AddForce(movement);
}
}
}

 

How high to jump?

 

Anything that fits on a mobile screen...