$A$ ball is thrown vertically upward,acceleration due to gravity is:

An object is placed one by one in three liquids having different densities. The object floats with $\frac{1}{9}$, $\frac{2}{11}$, and $\frac{3}{7}$ parts of its volume outside the liquid surface in liquids of densities $d_1$, $d_2$, and $d_3$ respectively. Which of the following statements is correct?

All the planets are moving in circular orbits. What provides the necessary force for this motion and what is the direction of this force? What will happen if this force disappears suddenly?

Consider Earth to be a homogeneous sphere. Scientist $A$ goes deep down in a mine and scientist $B$ goes high up in a balloon. The acceleration due to gravity as measured by:

$(a)$ The Earth is acted upon by the gravitation of the Sun,yet it does not fall into the Sun. Why?
$(b)$ An object of mass $500 \, g$ is dropped from a tower of height $5 \, m$. Calculate its momentum when it touches the ground (given $g = 10 \, m s^{-2}$).

On the Earth,a stone is thrown from a height in a direction parallel to the Earth's surface,while another stone is simultaneously dropped from the same height. Which stone would reach the ground first and why?