code

using UnityEngine;
using System.Collections;

public class MoveScript : MonoBehaviour {
	public float turnSpeed = 80.0f;
	public float forwardSpeed = 15.0f;
	public float maxSpeed = 80.0f;

	private Rigidbody rb;


	void Start ()
	{
		rb = GetComponent<Rigidbody>();

	}

	void FixedUpdate ()
	{


				float turnFactor = Input.GetAxis ("Horizontal");


				Vector3 moveDirection = new Vector3 (turnSpeed*turnFactor, 0.0f, 1.0f*forwardSpeed);



				rb.AddForce (moveDirection);



		//Limit speed
		if(rb.velocity.magnitude > maxSpeed)
		{
			rb.velocity = rb.velocity.normalized * maxSpeed;
		}
		Debug.Log (rb.velocity.magnitude);

	}





}