Question

a book applies its weight on a table. the normal reaction force is applied on book. So according to the third law of newton this object should be moving. why is it stationary?

Answer 1

If the book is kept on a flat table then the forces acting on the book are Balanced in nature.  

The weight of the book(=mg) acting downwards and the Normal Reaction acting upwards. The balanced nature of these 2 forces causes book to stay still on the table!

Answer 2

If the book is kept on a flat table then the forces acting on the book are Balanced in nature.  

The weight of the book(=mg) acting downwards and the Normal Reaction acting upwards. The balanced nature of these 2 forces causes book to stay still on the table!