If the distance between two masses is doubled,the gravitational attraction between them

Two bodies of masses $8 \,kg$ are placed at the vertices $A$ and $B$ of an equilateral triangle $ABC$. $A$ third body of mass $2 \,kg$ is placed at the centroid $G$ of the triangle. If $AG=BG=CG=1 \,m$, where should a fourth body of mass $4 \,kg$ be placed, so that the resultant force on the $2 \,kg$ body is zero?

We can shield a charge from electric fields by putting it inside a hollow conductor. Can we shield a body from the gravitational influence of nearby matter by putting it inside a hollow sphere or by some other means?

The gravitational constant depends upon .........

$A$ suitable unit for gravitational constant is

An astronaut of mass $m$ is working on a satellite orbiting the Earth at a distance $h$ from the Earth's surface. The radius of the Earth is $R$,while its mass is $M$. The gravitational pull $F_G$ on the astronaut is