Answer
(a) $r=3.46\times 10^8m$
(b) float rather than walk
Work Step by Step
(a) We can find the required distance as follows:
$r=\frac{R}{1+\sqrt{m_M/m_E}}$
We plug in the known values to obtain:
$r=\frac{3.84\times 10^8m}{1+\sqrt{7.35\times 10^{22}Kg/5.97\times 10^{24}Kg}}$
$r=3.46\times 10^8m$
(b) We know that the net gravitational force on the spaceship and astronauts decreases initially and then increases in the opposite direction. Thus, the astronauts appear to float, rather than walk.
