Question

(which statement is true)....As you sit in a chair at your computer, the chair exerts an upward supporting force n on you, and gravity exerts a downward force Fg on you. To a fairly good approximation, n =− Fg . Is this an example of Newton’s third law? 1.No;n+Fg ≈0 is due to the fact that your upward or downward acceleration happens to be almost negligible. 2.Yes; the “action” Fg must produce a “re-action” n . 3.Yes; your velocity happens to be zero. 4.Yes; the chair is attached to the earth, so both n and Fg are exerted by the earth.

Answer 1

no.

However, the explanation can be improved.

For a pair of forces to be considered an action-reaction pair,
it must satisfied 4 conditions:
(A) The magnitude of the forces are the same;
(B) The forces act in opposite direction
(C) The forces are of the same type
(D) The forces act on different objects.

For the question,
the 2 forces act on you.

Answer 2

wait a second.. it obviously is an action reaction pair.. HEll ANY FORCE WILL ALWAYS ALWAYS ALWAYS HAVE a reaction.. thats what newton's law is..

point number 2.. the force put by you on the chair.. NEED not be equal to the force of gravity.. .. but whatever force you are putting on chair.. REST ASSURE THAT THE CHAIR IS PUTTING EXACTLY.. EXACTLY the same force on you in the opposite direction

strictly speaking you are being accelerated cause of a) spin of earth b) revolution of earth c) revolution of the entire solar system ... .but inspite of that.. the force of you on the chair = the force of chair on you!!..

Answer 3

Ok so i guess. your real question is whether FORCE OF GRAVITY on you.. and the normal force on you are they action reaction? :D.. in that case.. Chongy is right :D.. kudos!