The Rigidbody we hit (Read Only). This is null if the object we hit is a collider with no rigidbody attached.
    // Make all rigidbodies we touch fly upwards
    function OnCollisionStay(collision : Collision) {
        // Check if the collider we hit has a rigidbody
        // Then apply the force
        if (collision.rigidbody) {
            collision.rigidbody.AddForce (Vector3.up * 15);
        }
    }
using UnityEngine; using System.Collections;
public class ExampleClass : MonoBehaviour { void OnCollisionStay(Collision collision) { if (collision.rigidbody) collision.rigidbody.AddForce(Vector3.up * 15); } }