PV S TR DR R _'. A student's head is bent over her physics boak. The head weighs P =43.5 N and is supported by the muscle force F _}. exerted hy the neck extensor muscles and by the contact force F . exerted at the atlantooccipital joint. Given that the _}. magnitude of F 5 is 60.0 N and is directed 35.0 below the horizontal. Find the direction of the contact force F.. . If the direction is below the horizontal, enter a negative value