Question

Billy is sitting in a chair in class. If the action force is the downward push of his weight on the chair, what is the reaction force?
A.
there is no reaction force
B.
the upward force of the Earth on Billy
C.
the downward force of Billy's weight on the Earth
D.
the upward force of the chair pushing on Billy

Answer 1

D. the upward force of the chair pushing on Billy.

By Newton's third law the downward force Billy exerts on the chair (his push) has an equal and opposite reaction: the chair pushes upward on Billy.