$A$ stone is dropped from the top of a tower. Its speed after it has fallen $20 \, m$ is (Take $g = 10 \, m s^{-2}$): (in $, m s^{-1}$)

Where will a body weigh more: $1 \, km$ above the surface of the earth or $1 \, km$ below the surface of the earth?

The weight of any person on the moon is about $1/6$ times that on the earth. He can lift a mass of $15\, kg$ on the earth. What will be the maximum mass,which can be lifted by the same force applied by the person on the moon (in $, kg$)?

Calculate the average density of the earth in terms of $g, G$ and $R$.

$A$ stone is dropped from a height of $20\, m$.
$(a)$ How long will it take to reach the ground?
$(b)$ What will be its speed when it hits the ground? $(g=10\, m s^{-2})$

What would be the effect on the weight of a body if the earth stopped rotating?