How to give jump without rigidboy by using transform?

I'm making a game where, when my game object collides with Right or Left wall, it gets jump effect. For that i am using rigidbody.addforce but problem is, when it collides with that wall while falling down, the physics engine also calculte its velocity so the effect of jump just doesn't work there. So i guess i have to remove rigidbody and work everything with transforms. But i don't really know how to do that. Any one out there? Here is my script.

public class MainScript : MonoBehaviour {

 public GameObject Ninja;
 public bool pingpong;

 Vector3 velocity;
 public float speed, jumpforce , forcefactor;
 float clickforce;

 void Start()
 {
     pingpong = true;
     velocity = Vector3.right;
 }

 void Update () 
 {
     if (pingpong) 
         {
             velocity = Vector3.left;
         } else 
         {
             velocity = Vector3.right;
     }

     if (Input.GetMouseButtonDown (0)) 
     {
          if(pingpong){
             
         Ninja.rigidbody.AddForce(new Vector3(jumpforce,jumpforce,0));
         }else{
             Ninja.rigidbody.AddForce(new Vector3(-jumpforce, jumpforce,0));
         }
     }
 }

 void OnCollisionEnter(Collision collision)
 {

     if (collision.collider.CompareTag ("Rwall"))
     {
         Ninja.rigidbody.AddForce(new Vector3(-jumpforce,jumpforce,0));
         pingpong = false;
     } else if (collision.collider.CompareTag ("Lwall"))
     {
         Ninja.rigidbody.AddForce(new Vector3(jumpforce,jumpforce,0));
         pingpong = true;
     }
 }

}