According to Kepler's second law, the radius vector to a planet from the Sun sweeps out equal areas in equal intervals of time. This law is a consequence of the conservation of ______________.

Explanation

To answer the question regarding Kepler's second law and its relation to conservation laws, we can break down the solution into the following steps:

### Step-by-Step Solution:

1. **Understanding Kepler's Second Law**:
- Kepler's second law states that a line segment joining a planet and the Sun sweeps out equal areas during equal intervals of time. This implies that the planet moves faster when it is closer to the Sun and slower when it is farther away.

2. **Concept of Areal Velocity**:
- The area swept out by the radius vector in a given time interval is called the areal velocity. According to Kepler's second law, this areal velocity remains constant for a planet in orbit around the Sun.

3. **Relating Areal Velocity to Angular Momentum**:
- The areal velocity (dA/dt) can be expressed in terms of angular momentum (L) and mass (m) of the planet. The relationship is given by:
\[ \text{Areal Velocity} = \frac{L}{2m} \]
- Here, L is the angular momentum of the planet about the Sun, and m is the mass of the planet.

4. **Conservation of Angular Momentum**:
- Since the areal velocity is constant, it implies that the angular momentum (L) of the planet is also constant. This constancy of angular momentum is a result of the conservation of angular momentum in a closed system where no external torques are acting.

5. **Conclusion**:
- Therefore, we conclude that Kepler's second law is a consequence of the conservation of angular momentum.

### Final Answer:
Kepler's second law is a consequence of the conservation of **angular momentum**.

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