title: When colliding, not changing the bool variable
body: <p>I am trying to write a script in C# for unity. This script is to make my sprite jump. I require the sprite to only able to jump when it is touching the ground, so when the bool 'isJumping' is set to false. </p>
  
  <p>When using the script in Unity3D (Although I'm using the 2D pre sets and am building a 2D game) I am able to jump when the game is first ran, but after hitting space the bool is set to true, and when I collide with the grounded which is tagged 'Ground' the bool does not get set to false meaning I can not jump again. </p>
  
  <p>So I am wondering what I have done wrong, and why when I collide with 'Ground' the bool is not set to false. Thank you for your help in advance! Below, is the code. :)</p>
  
  <pre class="lang-cs prettyprint-override"><code>using UnityEngine;
  using System.Collections;
  
  public class Jump1 : MonoBehaviour {
  
      public float jumpHeight;
      public bool isJumping = false;
  
      void Start() {
  
      }
  
      void Update() {
          if (Input.GetKeyDown(KeyCode.Space))
          {
              if (isJumping == false)
              {
                 rigidbody2D.AddForce(Vector2.up * jumpHeight);
                 isJumping = true;
              }
          }
      }
  
      void onCollisionEnter2D(Collision2D col) {
          if (col.gameObject.tag == "Ground")
          {
              isJumping = false;
          }
      }
  }
  </code></pre>