The correct option is **A. Electrostatic forces can be both attractive and repulsive, while gravitational forces are always attractive.** ### Detailed Explanation 1. **Understanding Electrostatic Forces:** - Electrostatic forces arise from the interaction between charged particles. According to Coulomb's Law, the force \( F \) between two point charges \( q_1 \) and \( q_2 \) separated by a distance \( r \) is given by: \[ F = k \frac{|q_1 q_2|}{r^2} \] where \( k \) is Coulomb's constant (\( 8.99 \times 10^9 \, \text{N m}^2/\text{C}^2 \)). - The nature of the force depends on the signs of the charges: - If both charges are of the same sign (both positive or both negative), the force is **repulsive**. - If the charges are of opposite signs (one positive and one negative), the force is **attractive**. 2. **Understanding Gravitational Forces:** - Gravitational forces, on the other hand, act between masses. According to Newton's Law of Universal Gravitation, the force \( F \) between two masses \( m_1 \) and \( m_2 \) separated by a distance \( r \) is given by: \[ F = G \frac{m_1 m_2}{r^2} \] where \( G \) is the gravitational constant (\( 6.674 \times 10^{-11} \, \text{N m}^2/\text{kg}^2 \)). - Gravitational forces are always **attractive**. This means that no matter the masses involved, they will always pull towards each other. 3. **Comparison of Forces:** - The key difference highlighted in option A is that electrostatic forces can either attract or repel depending on the nature of the charges, while gravitational forces can only attract. This fundamental difference is crucial in understanding how these forces operate in various physical situations. ### Why Other Options Are Incorrect - **Option B: Gravitational forces can be both attractive and repulsive, while electrostatic forces are always attractive.** - This statement is incorrect because gravitational forces are never repulsive; they only attract. Electrostatic forces can indeed be both attractive and repulsive, making this option false. - **Option C: 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 comparison at all distances without context. Gravitational forces become significant at large distances (like between celestial bodies), but they are still always weaker than electrostatic forces when comparing similar magnitudes of charge and mass. Thus, this option is not entirely accurate. - **Option D: Gravitational forces only act on charged particles, while electrostatic forces act on all masses.** - This statement is incorrect because gravitational forces act on all masses, regardless of charge. In contrast, electrostatic forces only act on charged particles. Therefore, this option misrepresents the nature of gravitational forces. ### Summary for Revision - **Electrostatic forces can be attractive or repulsive, depending on the charges involved.** - **Gravitational forces are always attractive and act between masses.** - **Electrostatic forces are significantly stronger than gravitational forces, but this strength varies with distance and context.** - **Gravitational forces act on all masses, while electrostatic forces act only on charged particles.** Understanding these differences is essential for grasping the fundamental concepts of forces in physics.