A book is lying on the table. What is the angle belween the action of the book on the table and the reaction of the table on the book?

Options

A. `0^(@)`
B. `45^(@)`
C. `90^(@)`
D. `180^(@)`

Answer

To solve the problem of finding the angle between the action of the book on the table and the reaction of the table on the book, we can follow these steps:

### Step 1: Identify the forces acting on the book
When a book is lying on a table, two main forces are acting on it:
- The weight of the book (denoted as \( W \) or \( Mg \)), which acts downwards due to gravity.
- The normal force (denoted as \( R \)), which is the reaction force exerted by the table on the book, acting upwards.

### Step 2: Understand the action-reaction pair
According to Newton's third law of motion, for every action, there is an equal and opposite reaction. In this case:
- The action is the force exerted by the book on the table (which is equal to the weight of the book acting downwards).
- The reaction is the force exerted by the table on the book (which acts upwards).

### Step 3: Determine the directions of the forces
- The weight of the book (\( Mg \)) acts vertically downward.
- The normal force (\( R \)) from the table acts vertically upward.

### Step 4: Calculate the angle between the action and reaction forces
Since the action (weight of the book) is directed downwards and the reaction (normal force from the table) is directed upwards, these two forces are in opposite directions.

### Step 5: Conclude the angle between the forces
The angle between two forces that act in exactly opposite directions is \( 180^\circ \).

### Final Answer
The angle between the action of the book on the table and the reaction of the table on the book is \( 180^\circ \).

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