Collision.relativeVelocity

public Vector3 relativeVelocity ;

説明

衝突した 2 つのオブジェクトの相対的な速度（読み取り専用）

// 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 OnCollisionEnter(Collision collision)
    {
        if (collision.relativeVelocity.magnitude > 2)
            audio.Play();
    }
}