Roll a Ball, sphere flies when I click play

I’ve just started learning Unity and I don’t know what’s going on cause when I write the script and press Play, everything works fine but the sphere keeps flying. The position of the sphere is how it’s taught in the video (x: 0, y:0.5, z:0) but when I click play It changes y=1. Can anybody help me?

Here is the script

using UnityEngine;
using System.Collections;

public class PlayerController : MonoBehaviour {

public float speed;

private Rigidbody rb;

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

void FixedUpdate ()
{
	float moveHorizontal = Input.GetAxis ("Horizontal");
	float moveVertical = Input.GetAxis ("Vertical");

	Vector3 movement = new Vector3 (moveHorizontal, 0.0f, moveVertical);

	rb.AddForce (movement * speed);
}

}

@LukeTheLukian I had this problem as well, I fixed it by selecting “Ground” (whatever you called your floor) under scene 1 and un-checking “Convex” which can be found in the “Mesh Collider” component.

Make sure in your rigidbody component “Is Kinematic” and “Use Gravity” settings match the tutorial.