Question

Which of the following quantities remain constant in a planetary system when seen from the surface of the sun.

• A. KE
• B. angular speed
• C. speed
• D. angular momentum
• E. binding energy

Answer 1

Answer: (D), (E)

The correct options are
D binding energy
E angular momentum

Option (D) and (E) are correct.

When observed from sun, there is no external torque or force on planet, so angular momentum of planet about sun will remain same. Also the total energy or binding energy of 'sun plus planet' system will remain same due to absence of any external force on 'sun plus planet' system.

Here speed as well as angular speed vary, due to elliptical path of planet, so kinetic energy also varies.