A projectile is thrown straight upward from the earth's surface with an initial speed \(V=\alpha V_E\), where \(\alpha\) is a constant and \(V_E\) is the escape speed. The projectile travels upto a height \(800 \, km\) from earth's surface before it comes to rest. The value of the constant \(\alpha\) is
\[
(\text{Radius of the earth} = 6400 \, km)
\]