_______ is a force that exists between any two objects in the universe.

Options

A. Frictional force
B. Electrostatic force
C. Muscular force
D. Gravitational force

Answer

**Step-by-Step Solution:**

1. **Understanding the Question**: The question asks for a specific type of force that exists between any two objects in the universe.

2. **Identifying the Force**: The force that acts between any two objects is known as the gravitational force. This force is present due to the masses of the objects and the distance between them.

3. **Explaining Gravitational Force**: Gravitational force (F) is proportional to the product of the masses of the two objects (m1 and m2) and inversely proportional to the square of the distance (r) between them. This relationship can be expressed mathematically as:
\[ F \propto \frac{m_1 \cdot m_2}{r^2} \]

4. **Introducing the Gravitational Constant**: To convert the proportionality into an equation, we introduce the gravitational constant (G). Thus, the formula for gravitational force becomes:
\[ F = G \frac{m_1 \cdot m_2}{r^2} \]
where G is the gravitational constant.

5. **Conclusion**: Therefore, the answer to the question is that the force that exists between any two objects in the universe is called the **gravitational force**.