Question

the value of g at height of 400 km above the surface​

Answer 1

There is a formula which determines that.

g=G*Mm/r

where g is force of gravity

G is the gravitational constant. it is equal to 6.67 * 10(to the power -11) {i forgot the unit but you can determine it by making G the subject}

M is mass of bigger body

m is mass of smaller body

r is distance between the radius of bodies.

I HOPE IT DOESEN"T HELP YOU. :-]]