# A 1.75 kg book is sitting on a stationary table. What is the magnitude and direction of the force exerted on the book by the table?

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The force exerted on the book by the table refers to the normal force  `F_N` .

Note that a normal force is always perpendicular to the surface of contact. It is always directed upward, too.

Since the book is lying on a stationary table which means that the surface is horizontal and not moving up or down. So normal force `(F_N)` is equal to downward force which is the weight `(W)` of the book.

Moreover, since the book is at rest the forces acting on the book are  `F_N` and `W` only.

Using Newton's Law,

`sum F = 0`

Since `F_N` is the upward force and `W` is the downard force, their signs differ.

`F_N - W=0`

`F_N= W`

Note that weight is the product of mass of an object and gravity. The value of gravity in earth is 9.8 m/s^2 .

`F_N=mg`

`F_N = (1.75 kg)(9.8 m/s^2) = 17.15 N`

Hence, the force exerted on the book by the table is 17.15 N and is directed upward.

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