RigidBody AddForce + Time.timeScale + Raycasts

Hi there ! First of all, I'm French, so if I do some errors, please don't care... I've made two scripts : One for slow-motion One other for shooting a gun with raycasts

I've seen here that Time.timeScale affects the AddForce() and that it's better to choose the velocity function : https://answers.unity.com/questions/1398963/rigidbodyaddforce-and-timetimescale.html

But, in my script, the Force is added by this :

 hit.rigidbody.AddForce(-hit.normal * impactForce);

So, I should create a Vector3 to replace AddForce, but, how to apply force on negative normal by Vector3 ?

Thanks you a lot,

Aubin