Question

What is the velocity of a satellite at a height 80 km from Earth, if the radius of Earth is 6400 km?

Answer 1

10840093 is the velocity

Answer 2

Here's the derivation first
Centripetel force balanced by gravitational force
v^2=GM/r
v=(GM/r)1/2
r=R+h
v=(GM/R+h)^1/2
So this is the derivation
Now coming to the question

(GM/R+h)^1/2
h<<R
(GM/R)^1/2
Now plug in the values of G,M,R to get the answer
To make it more simpler
put GM=gR^2
and get the equation simplified to
v=(gr)^1/2
Hope it helps
:)