The mass density of a spherical body is given by $\rho \left( r \right) = \frac{k}{r}$ for $r \leq R\,\,$ and $\rho \left( r \right) = 0\,$ for $r > R$ , where $r$ is the distance from the centre. The correct graph that describes qualitatively the acceleration, $a$, of a test particle as a function of $r$ is

What is weightlessness ? Explain with example.

If ${R}_{{E}}$ be the radius of Earth, then the ratio between the acceleration due to gravity at a depth $' {r} '$ below and a height $' r '$ above the earth surface is:

(Given : $\left.{r}<{R}_{{E}}\right)$

Which of the following symptoms is likely to afflict an astronaut in space $(a)$ swollen feet, $(b)$ swollen face, $(c)$ headache, $(d)$ orientational problem.

A body weighs $72\; N$ on the surface of the earth. What is the gravitational force on it, at a height equal to half the radius of the earth ?