The correct option is **D**: Both electrostatic and gravitational forces obey the inverse square law, but electrostatic forces can be either attractive or repulsive. ### Detailed Explanation: 1. **Understanding the Forces**: - **Electrostatic Forces**: These are the forces between charged particles. They can be either attractive or repulsive depending on the nature of the charges involved: - Like charges (e.g., two positive charges or two negative charges) repel each other. - Unlike charges (e.g., one positive and one negative charge) attract each other. - **Gravitational Forces**: These are the forces of attraction between masses. Gravitational forces are always attractive; they pull masses toward each other and never push them apart. 2. **Inverse Square Law**: - Both electrostatic and gravitational forces follow the inverse square law, which states that the force between two point-like objects is inversely proportional to the square of the distance between them. This can be mathematically expressed as: - For gravitational force: \( F_g = G \frac{m_1 m_2}{r^2} \) - For electrostatic force: \( F_e = k \frac{|q_1 q_2|}{r^2} \) - Here, \( G \) is the gravitational constant, \( k \) is Coulomb's constant, \( m_1 \) and \( m_2 \) are the masses of the objects, \( q_1 \) and \( q_2 \) are the charges, and \( r \) is the distance between the centers of the two objects. 3. **Why Option D is Correct**: - Option D accurately describes the nature of both forces: they both follow the inverse square law, and electrostatic forces can be either attractive or repulsive, depending on the charges involved. This is a fundamental characteristic of electrostatic interactions that distinguishes them from gravitational interactions. ### Why the Other Options are Incorrect: - **Option A**: "Electrostatic forces are always attractive, while gravitational forces can be both attractive and repulsive." - This statement is incorrect because electrostatic forces can be both attractive and repulsive, as explained above. Gravitational forces, on the other hand, are always attractive. - **Option B**: "Electrostatic forces are significantly stronger than gravitational forces at all distances." - While it is true that electrostatic forces are generally much stronger than gravitational forces, this statement is misleading because it implies a universal truth at all distances without context. The strength of the forces can vary based on the specific charges and masses involved, but electrostatic forces are indeed stronger in most practical scenarios. - **Option C**: "Gravitational forces depend on the charge of the objects, whereas electrostatic forces depend on their mass." - This statement is fundamentally incorrect. Gravitational forces depend on the mass of the objects, while electrostatic forces depend on the charge of the objects. This is a complete reversal of the actual definitions of these forces. ### Common Pitfalls: - Confusing the nature of the forces: Remember that gravitational forces are always attractive, while electrostatic forces can be both attractive and repulsive. - Misunderstanding the inverse square law: Ensure you understand how the distance affects the strength of both types of forces. - Overgeneralizing the strength of forces: While electrostatic forces are generally stronger, the context of the specific charges and masses must be considered. ### Revision Summary: - Electrostatic forces can be attractive or repulsive; gravitational forces are always attractive. - Both forces obey the inverse square law, which relates force strength to the distance between objects. - Gravitational forces depend on mass, while electrostatic forces depend on charge. - Understanding the fundamental differences and similarities between these forces is crucial for solving related problems in physics.