Question

When an object is in a circular orbit, which of the following quantities are constant?

The object's kinetic energy.The object's gravitational potential energy.The sum of the object's kinetic and gravitational potential energies.The object's momentum.The object's angular momentum.None of these.

b.)When an object is in an elliptical orbit, which of the following quantities are constant?

The sum of the object's kinetic and gravitational potential energies.The object's angular momentum.The object's momentum.The object's gravitational potential energy.The object's kinetic energy.None of these.

Answer 1

a) when object moves in a pure circular motion (radius constant considered) then correct options are-

Speed will be constant and that's why kinetic energy will be constant.

if radius doesn't change then gravitational potential energy will be constant.

as kinetic and potential energy are constant then sum of kinetic and potential energy will also be constant.

as speed and radius are not changing so angular momentum will be constant ( L= mvr).

b). when an object is in elliptical orbit, means radius is changing then correct options are-

sum of kinetic energy and potential energy will be constant

object's angular momentum will be conserved as no external torque acting on it.

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