Gravitation Questions

Suppose the charge of a proton and an electron differ slightly. One of them is $-e$, the other is $(e+\Delta e)$. If the net of electrostatic force and gravitational force between two hydrogen atoms placed at a distance $d$ (much greater than atomic size) apart is zero, then $\Delta e$ is of the order of [Given mass of hydrogen $m_h=1.67\times 10^{-27}\text{kg}$ ]:

The acceleration due to gravity at a height $1\text{km}$ above the earth is the same as at a depth $d$ below the surface of earth. Then:

Two astronauts are floating in gravitational free space after having lost contact with their spaceship. The two will: