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();
    }
}