OnTriggerEnter2D doesn't apply forces correctly,if at all

Problem:

I have a cluster of balloons in my scene in which I shoot darts at. Ideally I would like the balloon that was hit to

1. instantiate a particle effect to simulate a balloon pop

2. apply a force to its surroundings

3. Destroy the dart that hit the balloon

Eventually I'll have the balloon gameObject destroyed after all these steps are completed. so naturally I used OnTriggerEnter2D(Collider2D coll) but so far it seems like forces aren't being applied while in this function.

code

 void OnTriggerEnter2D(Collider2D coll)
 {

     if (coll.gameObject.tag == "Dart") 
     {
         Debug.Log("dart hit balloon!");
         isHitVector = new Vector3(coll.gameObject.transform.position.x, coll.gameObject.transform.position.y,10.0f);
         Rigidbody2DExtension.AddExplosionForces(gameObject.rigidbody2D,Power * 100,isHitVector,Radius);


         rigidbody2D.AddForce(transform.position);
         ParticleSystem p = Instantiate (balloonExplosionParticle, transform.position, Quaternion.identity) as ParticleSystem;

         isHit= true;

         //rigidbody2D.AddForce(Power*1000 *Vector3.one);
         Destroy (coll.gameObject);
     }

 }

  //Static method to apply an explosive force located in the Rigidbody2DExtension class 
  public static void AddExplosionForces (Rigidbody2D body, float expForce, Vector3 expPosition, float expRadius)
 {
     var dir = (body.transform.position - expPosition);
     float calc = 1 - (dir.magnitude / expRadius);
     if (calc <= 0) {
         calc = 0;        
     }
     
     body.AddForce (dir.normalized * expForce * calc);
 }

What I've noticed It seems that I am reaching the condition of that the dart is hitting the balloon as I'm able to print out "dart hit balloon!". I've noticed that if I were to add the Rigidbody2DExtension function in FixedUpdate (shown below) it works perfectly fine and does exactly what I want it to.

 void FixedUpdate()
     {
         if (Input.GetButtonDown("Fire1")){
             Vector3 mousePos = Input.mousePosition;
             mousePos.z = 10;
             Vector3 objPos1 = Camera.main.ScreenToWorldPoint(mousePos);
             Rigidbody2DExtension.AddExplosionForces(rigidbody2D, Power * 100, objPos1, Radius);
         }
     }

Main Question

Is there something I'm not seeing in using onTriggerEnter? It's behaving extremely strangely..