What is the time period of a seconds pendulum on a planet whose mass and radius are twice that of the Earth?

The mass of the moon is $7.34 \times 10^{22} \ kg$. If the acceleration due to gravity on the moon is $1.4 \ m/s^2$,calculate the radius of the moon. (Given: $G = 6.667 \times 10^{-11} \ N \cdot m^2/kg^2$)

At what height above the Earth's surface does the acceleration due to gravity become $1\%$ of its value at the Earth's surface (in $R$)? (Radius of Earth $= R$)

Neglecting air resistance,is the acceleration due to gravity the same for both heavy and light objects?

If the density of a planet is double that of the earth and the radius is $1.5$ times that of the earth,the acceleration due to gravity on the surface of the planet is ........

What should be the angular velocity of the Earth due to rotation about its own axis so that the weight of an object at the equator becomes $3/5$ of its initial value? (Radius of Earth at the equator is $R = 6400 \, km$,take $g = 10 \, m/s^2$)