Question

A book is resting on the surface of a table. Consider the following four forces that arise in this situation.

1. The force of the earth pulling on the book.
2. The force of the table pushing on the book.
3. The force of the book pushing on the table.
4. The force of the book pulling on the earth.

Based on the above information, answer the following questions:

Which two forces form an action-reaction pair?

1. $1and2$
2. $1and3$
3. $1and4$
4. $2and4$

Answer 1

According to Newton's third law, for every action, there is an equal and opposite reaction.

Let us analyze the four situations:

1. The force of the earth pulling on the book: For this situation, the equal and opposite reaction is the book pulling on the earth. Which is the fourth situation.
2. The force of the table pushing on the book: For this situation, the equal and opposite reaction is the book pushing on the table. Which is the third situation.
3. The force of the book pushing on the table: For this situation, the equal and opposite reaction is the table pushing on the book. Which is the second situation.
4. The force of the book pulling on the earth: For this situation, the equal and opposite reaction is the earth pulling on the book. Which is the first situation.

From this, the action-reaction pairs are $1-4and2-3$.

Hence, the two forces which form an action-reaction pair are option (c) $1and4$.