MouseDrag.cs

using UnityEngine;
using System.Collections;

public class MouseDrag : MonoBehaviour {

    public float distance;
    public int ballMass;
    public float offset;
    public float horizontalSpeed;
    public float verticalSpeed;

    void FixedUpdate() {
        //print (Input.mousePosition.x + "," + Input.mousePosition.y);
        Vector3 mousePosition = new Vector3 (Input.mousePosition.x, Input.mousePosition.y, distance);

        Vector3 objectPosition = Camera.main.ScreenToWorldPoint (mousePosition);

        transform.position = objectPosition;
    }

    /*
    void FixedUpdate() {
        float h = horizontalSpeed * Input.GetAxis ("Mouse X");
        float v = verticalSpeed * Input.GetAxis ("Mouse Y");
        Rigidbody rb = GetComponent<Rigidbody> ();
        rb.MovePosition (rb.position + transform.rotation * new Vector3 (v, h, 0));
    }
    */

    void OnCollisionEnter(Collision col) {
        if (col.gameObject.tag == "ball") {
            Debug.Log ("Strike");

            float force = col.relativeVelocity.sqrMagnitude * ballMass;

            Rigidbody rb = col.gameObject.GetComponent<Rigidbody>();
            rb.AddForce(transform.right * force);

        }
    }

}