Question

can anyone ans this guestion who is good in physics

Answer 1

take the gravity as 9.8 and then solve

Answer 2

equation to find g at height h above the surface
$\frac{g}{2} = g(1 - 2 \frac{h}{r} )$
where r is radius of Earth
1/2=1-2h/r
2h/r=1/2
h=r/4
i.e.one fourth of radius of Earth