Indicate the forces of action and reaction in the following cases:

(i) a man standing on the ground;

(ii) a stone suspended by a thread from the ceiling;

(iii) a book lying on the table;

(iv) motion of moon around the earth; and

(v) when a magnet attracts a piece of iron.

(i) A man standing on the ground:

The action force is when the man exerts a downward force equal to his weight on the ground. And, as a reaction, the ground exerts an equal upward force on the man. 

(ii) A stone suspended by a thread from the ceiling: 

The weight of the stone acts vertically downwards (action). A tension equal to the weight of the stone acts vertically upwards in the thread.

(iii) A book lying on the table: 

The book exerts a downward force equal to its weight on the table (action). The table exerts an equal force on the book in the upward direction (reaction).

(iv) Motion of moon around the earth: 

The moon attracts the earth with some force (action). The earth also attracts the moon with an equal and opposite force (reaction). Hence, it kees orbiting around the Earh. 

(v) When a magnet attracts a piece of iron:

When a magnet and a piece of iron are brought closer to each other, the magnet attracts the iron piece with a certain force (action). The iron piece also attracts the magnet with an equal and the opposite force (reaction).