rigidbody2d addforce for moving gameObject not work

Hi everyone. My english is bad, but I will try to tell you about my problem. Code (C#):

 void FixedUpdate () {
         on_tram = Physics2D.Linecast (on_tram_left.position, on_tram_right.position, 1<< LayerMask.NameToLayer("player_l"));
         Debug.DrawLine (on_tram_left.position, on_tram_right.position, Color.green);
         if(on_tram == true){
             on_tram = false;
             player_tram.rigidbody2D.velocity = Vector2.zero;
             player_tram.rigidbody2D.angularVelocity = 0f;
             Vector2 dir = (tram_vec.transform.position - player_tram.transform.position).normalized;
             Debug.Log(dir);
             player_tram.rigidbody2D.AddForce(dir*500f);
             Debug.DrawLine(player_tram.transform.position, tram_vec.transform.position, Color.green);
                       
         }
     }

So. When game in process and when player cross the line, player not "flying" to gameObject. It make small step in right/left side in moment and after that make ideal vertical jump. And I think player must "fly" for diagonal, but it move very strange. Help me please. You my last hope