When a car slams on breaks, a book in the seat of the car slides forward. What terms describes why that happens?​

Newton's first law which states that, if a body is at rest or moving at a constant speed in a straight line, it will remain at rest or keep moving in a straight line at constant speed unless it is acted upon by a force.

depends where

on my head

yes

on my legs

yes

on my

arms

yesh

allowed for the prediction of the properties of missing elements.