Answer
$2.65 ×10^6m$
Work Step by Step
Let 'd' be the altitude and 'm' be the mass of the body.
From Newton's law of universal gravitation
$F=\frac{GM_Em}{r^2}$
but $F=ma$
so
$ma=\frac{GM_Em}{r^2}$
$a=\frac{GM_E}{r^2}$
$r=\sqrt\frac{GM_E}{a}$
putting the we values, we get
$r=\sqrt\frac{6.67\times10^{-11}\times5.98\times10^{24}}{4.9}=9.02\times10^6m$
now we can find $'d'$that is altitude, it is the difference between$'r'$ and radius of earth $'r_E'$
$d=r-r_E$
putting the values we get
$d=9.02\times10^6-6.37\times10^6$
$d=2.65\times10^6m$
