Unity Bouncing Ball

ball.cs

using UnityEngine;
using System.Collections;

public class Ball : MonoBehaviour {

	private Paddle paddle;

	private Vector3 paddleToBallVector;

	private bool hasStarted = false;

	// Constant speed of the ball
    private float speed = 10f;
 
    // Keep track of the direction in which the ball is moving
    private Vector2 velocity;
 
    // used for velocity calculation
    private Vector2 lastPos;

	// Use this for initialization
	void Start () {
		paddle = GameObject.FindObjectOfType<Paddle>();
		paddleToBallVector = this.transform.position - paddle.transform.position;
	}
	
	// Update is called once per frame
	void Update () {
		if (!hasStarted) {
			// lock the ball relative to the paddle until mouse press launch.
			this.transform.position = paddle.transform.position + paddleToBallVector;
		}
		if (Input.GetMouseButtonDown (0)) {
			print("Lauch Ball");
			this.GetComponent<Rigidbody2D>().velocity = new Vector2(2f,10f);
			hasStarted = true;
		}
	}

	void OnCollisionEnter2D (Collision2D collision) {
		if (hasStarted) {
			//GetComponent<AudioSource> ().Play ();
			// Normal
	        Vector3 N = collision.contacts[0].normal;
	 
	        //Direction
	        Vector3 V = velocity.normalized;
	 
	        // Reflection
	        Vector3 R = Vector3.Reflect(V, N).normalized;
	 
	        // Assign normalized reflection with the constant speed
			GameObject.FindObjectOfType<Ball>().GetComponent<Rigidbody2D>().velocity = new Vector2(R.x, R.y) * speed;
		}
	}

	void FixedUpdate () {
        // Get pos 2d of the ball.
        Vector3 pos3D = transform.position;
        Vector2 pos2D = new Vector2(pos3D.x, pos3D.y);
 
        // Velocity calculation. Will be used for the bounce
        velocity = pos2D - lastPos;
        lastPos = pos2D;
    }
}