How to keep an object from speeding up or slowing down?

I'm making a pong game to learn the basics of how to make games. I'm almost done with the game but sometimes when the player hits the ball at a certain angle the ball speeds up or it slows down, how do I make it so that the ball is always going at a constant speed and it doesn't speed up or slow down?
here's the code for the ball.

 using System.Collections;
 using System.Collections.Generic;
 using UnityEngine;
 
 public class BallMovement : MonoBehaviour
 {
 
     private int playerScore;
     private int enemyScore;
     private int randomRotation;
 
     [SerializeField] private float launchPower = 500;
 
     private void Awake()
     {
         randomRotation = Random.Range(0, 361);
 
         if (randomRotation == 90 ||
             randomRotation == 180 ||
             randomRotation == 270)
         {
             randomRotation += 10;
         }
 
         GetComponent<Rigidbody2D>().SetRotation(90);
     }
 
     private void Update()
     {
         if (Input.GetKeyDown(KeyCode.Space))
         {
             GetComponent<Rigidbody2D>().AddForce(transform.up * launchPower);
         }
     }
 
     public void OnCollisionEnter2D(Collision2D collision)
     {
         EnemyGoal enemyGoal = collision.collider.GetComponent<EnemyGoal>();
         PlayerGoal playerGoal = collision.collider.GetComponent<PlayerGoal>();
 
         if (playerGoal != null)
         {
             enemyScore++;
         }
 
         if (enemyGoal != null)
         {
             playerScore++;
         }
     }
 }