Question

A small moon is in a circular orbit around an exoplanet. It orbits at an altitude of 700 km. This exoplanet is the same size as Earth, but is only 1/2 as dense.Does this exoplanet exert a torque on its moon? Why or why not?No, because the force exerted by the planet on the meteoroid has a negligible magnitude.Yes, because the meteoroid's direction of motion is constantly changing.Yes, because the planet exerts a centripetal force on the meteoroid.No, because the planet exerts a force on the meteoroid parallel to its position vector relative to the center of mass of the planet.

Answer 1

According to kepler's 2nd law a planet sweeps equal area in equal time around a planet.

here the angular momentum of planet is constant

if angular momentum is constant then according to conservation of angular momentum the net torque on the moon due to the exoplanet will be equal to 0.

So here the net torque = 0.

That's why last option is correct.