title: rigidbody.AddForce affects all game objects with the same script component
body: <p>on scene I have 3 balls with Ball.cs script attached to each of them. And when I push ball with mouse all balls start moving, but I need that only one that I touch moves.</p>
  
  <p>Here is my FixedUpdate:</p>
  
  <pre><code>void FixedUpdate() {
      if(!isMoving) {
  
          if (Input.GetMouseButtonDown (0)) {
  
              Ray ray = Camera.main.ScreenPointToRay(Input.mousePosition);
              RaycastHit hit;
              if (Physics.Raycast(ray, out hit, 100)) {
                  if(hit.collider.tag == "Ball") {
                      startPos = hit.point;
                  }
              }
          }
  
          if (startPos != Vector3.zero &amp;&amp; Input.GetMouseButtonUp(0)) {
              endPos = Camera.main.ScreenToWorldPoint(Input.mousePosition);
  
              Vector3 direction = endPos - startPos;
              direction.Normalize();
  
              float distance = Vector3.Distance(endPos, startPos);
  
              rigidbody.AddForce(direction * distance * force * Time.deltaTime, ForceMode.Impulse);
  
              isMoving = true;
          }
      } else {
          if(rigidbody.velocity.sqrMagnitude == 0) {
              isMoving = false;
              startPos = endPos = Vector3.zero;
          }
      }
  }
  </code></pre>