物理学，倾斜表面上的轮子

Question

我想编写物理学的某些部分。我有一个轮子和一个倾斜的表面。当轮子落在表面上时，它应该沿着那个表面移动。 我知道如何在车轮落在地面上之后计算机芯的力和方向，但是在这之后车轮应该如何表现？

这是我目前的代码

using UnityEngine;

public class MyPhysics : MonoBehaviour
{

public LayerMask lMask;
public Rigidbody2D ball;
public CircleCollider2D circle;
public Vector2 gravity;
public Vector2 velocity;
public float mass = 1;
public Vector2 a;
public bool simulate = true;

private Vector2 weight;
private float radius;


// Use this for initialization
void Start()
{
    radius = ball.transform.localScale.x * circle.radius;
    weight = mass * gravity;
}

// Update is called once per frame
void Update()
{
    if (simulate)
        DoAllShit();
}

void DoAllShit()
{
    a += (gravity * Time.deltaTime);
    velocity = (velocity + a);

    RaycastHit2D hit = Physics2D.Raycast(ball.position, velocity.normalized, velocity.magnitude + radius, lMask);
    if (hit)
    {
        float angle = Vector2.Angle(hit.normal, velocity) - 90;
        // Debug.Log("angle: " + angle);
        float magnitude = velocity.magnitude * Mathf.Cos(Mathf.Deg2Rad * angle);
        // Debug.Log("magnitude of velocity: " + velocity.magnitude + "  magnitude of cos: " + magnitude);
        Vector2 rotatedVector = GetPerp(hit.normal, velocity);
        Vector2 newVector = magnitude * rotatedVector;
        Debug.DrawLine(hit.point, hit.point + rotatedVector, Color.blue, float.MaxValue);
        Debug.Log("normal: " + hit.normal + "  rotated vector: " + rotatedVector + " velocity: " + velocity);
        Debug.DrawLine(hit.point + hit.normal * 0.1f, hit.point + hit.normal * 0.1f + newVector, Color.red, float.MaxValue);
        velocity = newVector;
        ball.position = velocity + (hit.normal * radius + hit.point);
        //simulate = false;
    }
    else
    {
        Debug.DrawLine(ball.position, ball.position + velocity.normalized * (velocity.magnitude + radius), Color.green, float.MaxValue);
        ball.position += (velocity);
    }
}

Vector2 GetPerp(Vector2 normal, Vector2 velocity)
{
    Vector2 perp;
    if (velocity.y <= 0)
    {
        normal.y *= -1;
    }
    else
    {
        normal.x *= -1;
    }
    perp.x = normal.y;
    perp.y = normal.x;

    return perp;
}

}