Question

For a planet moving around the sun in an elliptical orbit, which of the following quantities remain constant?

• A. The total energy of the sun planet system
• B. The angular momentum of the planet about the sun.
• C. The force of attraction between the two
• D. The linear momentum of the planet

Answer 1

Answer: (A), (B)

The correct options are
A The total energy of the sun planet system
B The angular momentum of the planet about the sun.

$1.$ Energy of the sun planet system is constant.
$2.$ According to Kepler's law of periods, angular momentum is also constant.
whereas the force of attraction keeps changing, because the distance between the sun and the planet is not constant.
Since the planet is moving in elliptical orbit, it's velocity keeps changing from point to point, hence linear momentum is not constant.