What Is the Reaction Force to Gravity on a Book Resting on a Shelf?

[steve0827]

Homework Statement

a book restson the shelf of a bookcase. the reaction force to the force of gravity acting on the book is?
A.)the weight of the book
B.)none of these
C.)the force of the shelf holding the book up
D.)the frictional force between the book and shelf
E.)the force exerted by the book on the earth

Homework Equations

N/A

The Attempt at a Solution

I thought the answer was C...but i was wrong.


i really need help on this

 

[marlon]

First question : how would you calculate the reaction force ? Imagine the book has a certain mass equal to 1 kg or whatever.

Draw a free body diagram and apply Newton's second law.

marlon

 

[steve0827]

i think its either A or B
could you give me a hint if those are right :P

 

[marlon]

i think its either A or B
could you give me a hint if those are right :P

No hints, that doesn't help you.

Why do you think it's A or B ?

marlon

 

[Doc Al]

the reaction force to the force of gravity acting on the book is?

Note that "reaction force" here is used in the Newton's 3rd law sense of "action/reaction".

Hint: What two bodies are involved in this interaction?

What does Newton's 3rd law say when two bodies interact?