Newton's third law and action-reaction pairs · CAP 2005 #2

Physics · mechanics

Problem

A physics textbook of mass

m

rests flat on a horizontal table of mass

M

placed on the ground. Let

N_{a\rightarrow b}

be the contact force exerted by body "a" on body "b". According to Newton's 3rd Law, which of the following is an action-reaction pair of forces? (a)

mg

and

N_{table\rightarrow book}

; (b)

(m+M)g

and

N_{table\rightarrow book}

; (c)

N_{ground\rightarrow table}

and

Mg + N_{book\rightarrow table}

; (d)

N_{ground\rightarrow table}

and

N_{table\rightarrow ground}