Why is my object tilting when moving?

Questions & Answers
1

Hello. I am using addRelativeForce to control a rectangle collider. However, it tilts whenever it is supposed to only move forward. How do I prevent this?

var forwardMoveAmount = -30; //Sets forward  speed.
var turnForce = 2; //Sets turning speed.
var canDrive = 0;//Sets up ground detection (For now, works with all objects)

function Start () 
{ 
	rigidbody.centerOfMass = Vector3 (0, 0, 0);//Keeps object upright. 
}

function OnCollisionEnter (col : Collision)
{
	canDrive = 1;//Gives player control entering on ground.
	if (col.gameObject.name == "GoingUp")//Check if on a jump pad.
    {
        rigidbody.velocity = (Vector3.up * 30);//Makes player fly upwards. 
	}
}
function OnCollisionStay (col : Collision)//Gives player control on ground.
{
	canDrive = 1;
}


function OnCollisionExit (col : Collision)//Removes player control off ground
{
	canDrive = 0;
}

function Update () {

	var forwardMoveAmount = Input.GetAxis("Vertical") * forwardMoveAmount * canDrive;//Get input, multiplies it by movement amount and if the player can drive. 
	var turnForce = Input.GetAxis("Horizontal") * turnForce;//Get input and multiplies it by turnFroce
	transform.Rotate (0,turnForce * canDrive,0);//Rotates if canDrive is not 0
	rigidbody.AddRelativeForce (Vector3.right * forwardMoveAmount);//Applies relative force to object to move it
}

Here is my whole player code in case it helps. Apologies if its a bit unprofessional, I’m quite new to unity.

2

You can prevent the rigidbody from rotating by setting its Freeze Rotation parameter in the Inspector tab.

3

The friction of the ground was rubbing on the collider. Sorry for necroposting, but someone helped me over on reddit. Thanks though!