An artificial satellite circles around the earth at the height where the gravitational force is one fourth of that at earth's surface. If the earth's radius is R the height of the satellite above the surface of the earth is?

Answer 1

r and Re

F = G Mm/r^2 = (.25) G Mm/Re^2
or
.25/Re^2 =1/r^2

.25 r^2 = Re^2

.5 r = Re
r = 2 Re
height = 2Re-Re = Re