Collision2D.relativeVelocity

public Vector2 relativeVelocity ;

Description

Относительная линейная скорость двух столкнувшихся объектов (Read Only).

// Play a sound when we hit an object with a big velocity
using UnityEngine;
using System.Collections;

public class ExampleClass : MonoBehaviour {
	AudioSource audio;
	
	void Start() {
		audio = GetComponent<AudioSource>();
	}
	
    void OnCollisionEnter2D(Collision2D collision) {
        if (collision.relativeVelocity.magnitude > 2)
            audio.Play();
    }
}