Explain why you feel Earth's gravitational force but not the gravitational force exerted by a book?

Answer 1

Because there's such a difference between the strengths of the two forces.

The gravitational force between two masses is proportional to the product of the masses.
So if one mass is constant, then the force is proportional to the other mass. Also, the force
is inversely proportional to the square of the distance between the two masses.

Let's say the book has a mass of 1 kg, and is one meter from you.

The earth's mass is 5.97 x 1024 kg, and it's centered 6,378,000 meters from you (earth's radius).

So the ratio of the (gravitational force toward the earth) to the (gravitational force toward the book) is

(5.97 x 1024)/ (6.378 x 106)2 = 1.468 x 1011

The gravitational force between you and the earth is about 147 billion times as strong as
the force between you and the book !

If you weigh a ton (2,000 lbs), then the force between you and the book is like 0.000000218 ounce.

Answer 2

You feel Earth's gravitational force because Earth has a much larger mass compared to you. The force of gravity between two objects depends on their masses and distance. Since the book is much lighter than Earth, the gravitational force it exerts on you is negligible compared to Earth's gravitational pull.