How to Increase speed of the ball over time?

I'm trying to make a Brick Breaker game and I want to speed up the ball's movement over time. Now I've wrote the code for it, but it doesn't effect the ball's movement. In the inspector ball's speed increases, but not in the game. What am I doing wrong? Why the code doesn't effect the ball in the game?


Ball's Script:

using System.Collections;
using System.Collections.Generic;
using UnityEngine;

public class Ball : MonoBehaviour {

private Rigidbody2D rb;
public float ballSpeed = 400;
public bool ballMoving;
public Transform ballPos;
public float maxBallSpeed = 1000f;

private void Awake()
{
rb = GetComponent<Rigidbody2D>();
}

// Use this for initialization
void Start () {

}

// Update is called once per frame
void Update () {

if(ballMoving == false)
{
transform.position = ballPos.position;
}

if (Input.GetButtonDown("Jump") & ballMoving == false)
{
ballMoving = true;
rb.AddForce(Vector2.up * ballSpeed);
}

// Increase ball movement over time
if(ballMoving == true)
{
ballSpeed += 20f;

if (ballSpeed >= maxBallSpeed)
{
ballSpeed = maxBallSpeed;
}
}
}