85.4 Some topics of discussion 2. Noninertial reference frames Alice Bob Newton's law is not valid in the car 85.4 Some topics of discussion B O47 §5.4 Some topics of discussion 2. Noninertial reference frames Alice Bob a0 r N mg A ? Newton’s law is not valid in the car. A 0 a r A B m mg N 0 a r B mg m N §5.4 Some topics of discussion