please help i get error saying Object reference not set to an instance of an object

using UnityEngine;
using System.Collections;

public class playerControler : MonoBehaviour {

private Rigidbody rb;

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

}
void FixedUpdate()
{
	float moveH = Input.GetAxis("Horizontal");
	float moveV = Input.GetAxis ("Vertical");

	Vector3 movement = new Vector3(moveH,0.0f,moveV);

	rb.AddForce(movement);

}

}

Your Start() method is misspelled with a non-capital “s” so rb will never get a value and will stay “null”.

therefore rb.AddForce(movement); will throw a null reference error