Unity Roll A ball Tutorial Jump Lag.

So, I've just started learning the unity engine and wanted to expand the first project a little to in-cooperate jumping. From guesswork and referring to the documentation i managed to come to this solution. However i noticed the ball would frequently ignore requests to jump. How should i change this such that The player can jump onto objects within a 3D world without any 'Input lag'

Code (CSharp):

1. using System.Collections;
2. using System.Collections.Generic;
3. using UnityEngine;
4. using UnityEngine.UI;
5.  
6. public class PlayerControl : MonoBehaviour {
7.    
8.     public float speed;
9.     public Text countText;
10.     public Text winText;
11.     public int CollectableNum;
12.     public float jumpForce;
13.  
14.     private Rigidbody rb;
15.     private int count;
16.     private bool hasJumped = false;
17.     private bool isGrounded = true;
18.  
19.     void Start ()
20.     {
21.         rb = GetComponent<Rigidbody> ();
22.         count = 0;
23.         SetCountText();
24.         winText.text = "";
25.     }
26.     void FixedUpdate()
27.     {
28.         float moveHorizontal = Input.GetAxis ("Horizontal");
29.         float moveVertical = Input.GetAxis ("Vertical");
30.  
31.         Vector3 movement = new Vector3 (moveHorizontal, 0.0f, moveVertical);
32.         rb.AddForce (movement * speed);
33.  
34.  
35.     }
36.  
37.     void OnCollisionStay(Collision other)
38.     {
39.         if (other.gameObject.CompareTag ("Ground/Object"))
40.         {
41.             if (Input.GetKeyDown ("space"))
42.             {
43.                 rb.AddForce (0, jumpForce, 0, ForceMode.Impulse);
44.             }
45.         }
46.     }
47.  
48.  
49.     void OnTriggerEnter(Collider other)
50.     {
51.         if (other.gameObject.CompareTag ("Pickup"))
52.         {
53.             other.gameObject.SetActive (false);
54.             count = count + 1;
55.             SetCountText ();
56.         }
57.     }
58.     void SetCountText ()
59.     {
60.         countText.text = "Count: " + count.ToString ();
61.         if (count >= CollectableNum)
62.         {
63.             winText.text = "You Win!";
64.         }
65.     }
66. }
67.