Shoot player away after loading force.

Dear unity community,

I am trying to shoot away my player after loading an amount of force by holding down a button, I am a student just starting with C#.

So basically, if I hold down the space bar, it will load force, when I release space bar the player should shoot away with the force given. Compare it with a catapult shooting a rock away.

I tried the following, but with this I can only fly with the player by holding down the space bar.I know the script doesn't do anything after releasing space, but what I tried didn't work so I left it out.

 using UnityEngine;
 using System.Collections;
 
 public class playerShoot: MonoBehaviour {
 
 
     public float maxCharge = 50.0f;
     public float JForce = 10.0f;
     public float increaseForce = 10.0f;
     public float chargeSpeed = 10.0f;
     public float resetSpeed = 10.0f;
     public float sidewaySpeed = 10.0f;
     
 
 
     // Use this for initialization
     void Start () {
     
     }
     
     // Update is called once per frame
     void Update () {
 
         increasePower ();
         if (Input.GetKey (KeyCode.Space)) {
             rigidbody2D.AddForce (new Vector2 (sidewaySpeed, JForce));
                 }
 
 }
 
     void increasePower () {
         if (Input.GetButton("Increase")) {
             JForce += Time.deltaTime * chargeSpeed;
             Debug.Log (JForce);
 
             JForce = Mathf.Clamp(JForce, 0, maxCharge);
 
                 }
         if (Input.GetButtonUp("Jump")) {
             JForce = resetSpeed;
             Debug.Log (JForce + "Force reseted");
         
 
         }
 
         
 }
 
 }
                 
 

Thank you in advance for helping me!

Kind regards,

Marijn