If the density of a planet is doubled without changing its radius,how does $g$ on the planet change?

An object weighs $10 \, N$ in air. When immersed fully in water,it weighs only $8 \, N$. The weight of the liquid displaced by the object will be (in $, N$)

Identical packets are dropped from two aeroplanes,one above the equator and the other above the north pole,both at height $h$. Assuming all conditions are identical,will those packets take the same time to reach the surface of the Earth? Justify your answer.

If a planet existed whose mass and radius were both half that of the Earth,the acceleration due to gravity at its surface would be: (in $, m s^{-2}$)

An object has a mass of $30 \ kg$. What is its weight $(i)$ on the moon $(ii)$ on another planet? The value of $g$ on the moon is $1/6$ the value of $g$ on the earth. The value of $g$ on the planet is $3$ times the value of $g$ on the earth. Take $g_{earth} = 10 \ m/s^2$.

In vacuum,all freely falling objects: