Forces which obey inverse square law are

Options

A. Gravitational forces
B. Electromagnetic forces
C. Nuclear forces
D. Both (1) & (2)

Answer

To determine which forces obey the inverse square law, we can analyze the definitions and characteristics of various fundamental forces. The inverse square law states that the force between two particles is inversely proportional to the square of the distance between them. Mathematically, this can be expressed as:

\[ F \propto \frac{1}{R^2} \]

where \( F \) is the force and \( R \) is the distance between the two particles.

### Step-by-Step Solution:

1. **Understand the Inverse Square Law**:
- The inverse square law implies that as the distance \( R \) between two objects increases, the force \( F \) decreases with the square of that distance. This means if you double the distance, the force becomes one-fourth.

**Hint**: Remember that the relationship is \( F \propto \frac{1}{R^2} \).

2. **Identify the Gravitational Force**:
- The gravitational force between two masses \( m_1 \) and \( m_2 \) is given by Newton's law of gravitation:
\[ F = G \frac{m_1 m_2}{R^2} \]
- Here, \( G \) is the gravitational constant. This clearly shows that gravitational force follows the inverse square law.

**Hint**: Look for the formula that includes mass and distance squared in the denominator.

3. **Identify the Electromagnetic Force**:
- According to Coulomb's law, the force \( F \) between two charges \( q_1 \) and \( q_2 \) is given by:
\[ F = k \frac{q_1 q_2}{R^2} \]
- Here, \( k \) is Coulomb's constant. This also demonstrates that the electromagnetic force follows the inverse square law.

**Hint**: Check for a similar formula involving charges and distance squared in the denominator.

4. **Consider the Nuclear Force**:
- The nuclear force acts between nucleons (protons and neutrons) within an atomic nucleus. Unlike gravitational and electromagnetic forces, the nuclear force does not follow the inverse square law. It is a short-range force and does not depend on the distance in the same way.

**Hint**: Remember that nuclear forces are not dependent on distance in the same manner as gravitational and electromagnetic forces.

5. **Conclusion**:
- From the analysis, we conclude that the forces that obey the inverse square law are:
- Gravitational force
- Electromagnetic force
- Therefore, the correct options are both 1 and 2.

**Final Answer**: The forces which obey the inverse square law are gravitational force and electromagnetic force.