Question

Two boys wearing in-line skates are standing on a surface with the palms of their hands touching and their arms bent, as shown in the figure. If Boy X pushes by straightening his arms out while Boy Y holds his arms in the original position, what is the motion of the two boys?

• A. Boy X does not move and Boy Y moves backward.
• B. Boy Y does not move and Boy X moves backward.
• C. Boy X and Boy Y both move backward
• D. Both boys fall down

Answer 1

The correct option is C Boy X and Boy Y both move backward

When Boy X pushes Y, Y moves backward because the push on Y by X is the only force acting on him. Similarly, since every action has an equal and opposite reaction, the force exerted by boy X on Y has the same effect on X, thus pushing X backward as well. Presence of friction help the boys move backward.