Question

When you push downward on a book at rest on a table, you feel an upward force. Does this force depend on friction? Defend your answer.

Answer 1

Answer:

No

Explanation:

We can explain the upward force in terms of Newton's third law, which states:

"when an object A exerts a force (action) on object B, then object B exerts an equal and opposite force (reaction) on object A"

If we apply this law to the situation described in the problem, the push you apply downward is the action, while the upward force exerted by the book on you is the reaction.

This reaction does not depend on the friction. In fact, friction acts whenever you try to move an object along a surface, in a direction parallel to the surface itself. In this case, instead, you are trying to push the object perpendicularly to the surface, not parallel: so, no friction acts when you push. The reaction force is mainly due to the normal reaction of the table on the book, that "pushes" the book upward, balancing the downward force and keeping the book at rest.