The value of acceleration due to gravity at Earth's surface is \(9.8ms^{-2}\). The altitude above its surface at which the acceleration due to gravity decreases to \(4.9ms^{-2}\), is close to :
(Radius of earth = \(6.4 \times 10^6m\))
1
\(1.6 \times 10^6m\)
2
\(6.4 \times 10^6m\)
3
\(9.0 \times 10^6m\)
4
\(2.6 \times 10^6m\)