Brackeys Fruit Ninja Velocity-Based Slicing

public class Blade : MonoBehaviour
{

    public Vector3 velocity {
        get;
        private set;
    }

    //other stuff in the class

    void UpdateCut() {
        Vector2 newPosition = cam.ScreenToWorldPoint(Input.mousePosition);
        rb.position = newPosition;

        //here is what's changed
        velocity = (newPosition - previousPosition);
        float distance = velocity.magnitude;
        //everything else is the same
        float speed = distance / Time.deltaTime;
        if (speed > minCuttingVelocity) {
            col.enabled = true;
        } else {
            col.enabled = false;
        }

        previousPosition = newPosition;
    }

}

//the other script
public class Fruit : MonoBehaviour
{

    //other stuff

    void OnTriggerEnter2D(Collider2D col) {
        if (col.tag == "Blade") {
            //changed stuff
            Blade blade = col.GetComponent<Blade>();
            Vector3 direction = ((blade != null) ? blade.velocity : col.transform.position - transform.position).normalized;
            //everything else is the same
            Quaternion rotation = Quaternion.LookRotation(direction);

            GameObject slicedFruit = Instantiate(fruitSlicedPrefab, transform.position, rotation);
            Destroy(gameObject);
        }
    }

}