# At what height above the surface of the earth will the acceleration due to gravity be 25%of its value on the surface of the earth?assume that the radius of the earth is 6400km.

R=6400 km

g'/g=R

^{2}/(R+h)

^{2}

[(25/100)g/g]

^{1/2}=R/(R+h)

5/10=R/(R+h)

2R = R+h

R=h

so, h=6400 km

**
**