How to check if an object hits the ground hard enough then add explosive force around it (2D)

Questions & Answers
1

Hello! I am trying to create my first every 2D game. The problem I am having at the moment is trying to add force to my character if my enemy jumps and lands hard enough. I know how to deal damage to the player but I need to know how to add a force to “push” the player back if they are close enough to the enemy.

I tried using onCollisionsEnter2D but it calls it every single time even if the enemy is just moving. I want it to detect once it hits the ground hard enough.

    private void OnCollisionEnter2D(Collision2D collision)
    {
        if(collision.gameObject.tag == "Ground")
        {
            foreach (Collider2D Obj in Physics2D.OverlapCircleAll(transform.position, radius))
            {
                if (Obj.GetComponent<Rigidbody2D>() != null && Obj.gameObject != gameObject)
                {
                    Debug.Log("Calling Function");
                    Rigidbody2D rb = Obj.GetComponent<Rigidbody2D>();
                    ExplosionForce2D forceScript = GetComponent<ExplosionForce2D>();
                    forceScript.AddExplosionForce(rb, force, transform.position, radius);
                }
            }
        }
    }

This is the function I am calling to add the force

public class ExplosionForce2D : MonoBehaviour
{
	public void AddExplosionForce (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);
	}
}
2

You probably want to check Collision.relativeVelocity:

void OnCollisionEnter (Collision collision)
{
    if (collision.gameObject.tag == "Ground")
    {
        if (collision.relativeVelocity >= 2)
        {
            foreach (Collider2D Obj in Physics2D.OverlapCircleAll (transform.position, radius))
            {
                // ..
            }
        }
    }
}