Ball.cs

using UnityEngine;
using System.Collections;
using UnityEngine.UI;

public class Ball : MonoBehaviour {

	//public float initialForce = 20.0f;
	public Vector3 launchVelocity;
	public bool ballLoaded;
	private Rigidbody rgdbdy;
	private AudioSource ballSound;
	private float laneWidth;
	private GameObject slider;

	void Awake ()
	{
		rgdbdy = gameObject.GetComponent<Rigidbody>();
		rgdbdy.useGravity = false;

		slider = GameObject.Find("BallSlider");
		laneWidth = GameObject.Find("Lane").transform.localScale.x;
	}

	void Start () 
	{
		ballLoaded = true;
	}

	public void Nudge ()
	{
		if (ballLoaded)
		{
			float value = slider.GetComponent<Slider>().value;
			float xPos = value * laneWidth / 2.0f ;
			transform.position = new Vector3 (xPos, transform.position.y, transform.position.z);
		}
	}

	public void Launch (Vector3 velocity)
	{
		if (ballLoaded)
		{
			rgdbdy.useGravity = true;
			rgdbdy.velocity = velocity;

			ballSound = GetComponent<AudioSource>();
			ballSound.Play (); // should be in on collision enter? or add a delay.

			ballLoaded = false;
		}
	}
}