Two boxes, A and B, are connected by a horizontal string S on a horizontal floor. A very light wire pulls horizontally on box B, as shown in the figure, with a force of 100 N. The reaction force to this pull is
A)the pull that box B exerts on string S.
B)the pull that string S exerts on box B.
C)the pull that string S exerts on box A.
D)the pull of box B on the wire.
E)the force that box A exerts on box B.

Question

Two boxes, A and B, are connected by a horizontal string S on a horizontal floor. A very light wire pulls horizontally on box B, as shown in the figure, with a force of 100 N. The reaction force to this pull is 
A)the pull that box B exerts on string S. 
B)the pull that string S exerts on box B. 
C)the pull that string S exerts on box A. 
D)the pull of box B on the wire. 
E)the force that box A exerts on box B.

Quizplus · Accepted Answer

The Answer of Two boxes, A and B, are connected by a horizontal string S on a horizontal floor. A very light wire pulls horizontally on box B, as shown in the figure, with a force of 100 N. The reaction force to this pull is 
A)the pull that box B exerts on string S. 
B)the pull that string S exerts on box B. 
C)the pull that string S exerts on box A. 
D)the pull of box B on the wire. 
E)the force that box A exerts on box B.

Two Boxes, a and B, Are Connected by a Horizontal