For a book of mass m, moving a distance d on a smooth horizontal table, the work done due to gravitational force is:

Correct option is C

​The correct answer is (c) 0

Explanation:

Work done by a force is given by the formula:

         $$W = F \cdot d \cdot \cos \theta$$​​

where:

• W = Work done
• F = Force applied
• d = Displacement
• $$\theta$$​ = Angle between force and displacement

In this case:

• The gravitational force acts vertically downward (towards the center of the Earth).
• The displacement of the book is horizontal along the table.
• The angle $$\theta$$​between the gravitational force and displacement is 90°.
• Since $$cos 90^\circ = 0$$​, the work done by the gravitational force is:

                                       $$W = mg \cdot d \cdot \cos 90^\circ = mgd \times 0 = 0$$​​

Thus, the work done by gravity is zero, as gravity does not contribute to the horizontal motion of the book.

Information Booster:

• Positive work: When force and displacement are in the same direction (e.g., lifting an object upward).
• Negative work: When force and displacement are in opposite directions (e.g., friction opposing motion).
• Zero work: When force is perpendicular to displacement or when no displacement occurs (e.g., carrying a bag horizontally while gravity acts vertically).