Keyboard Input

I am watching this basic tutorial https://unity3d.com/learn/tutorials/projects/roll-ball-tutorial/moving-player?playlist=17141 , i had written the code to move the player , but the player is not moving.

The ball is not moving - Check the code below :

using UnityEngine;

using System.Collections;

public class Playercontroller : MonoBehaviour {

 public float speed;

 private Rigidbody rb;

 // Use this for initialization
 void Start () {
     rb = GetComponent<Rigidbody> ();
 }
 // Update is called once per frame
 void Fixedupdate () {
     float moveHorizontal = Input.GetAxis ("Horizontal");
     float moveVertical = Input.GetAxis ("Vertical");

     Vector3 movement = new Vector3 (moveHorizontal, 0.0f, moveVertical);

     rb.AddForce (movement * speed);
 
 }

}