A body weight 63N on the surface of the earth. What is the gravitational force on it due to the earth at a height equal to half the radius of the earth.

Explanation

Let R = radius of the earth
So, distance of the body from the centre of the earth in the first case, `r_1=R` and that is the second case,
`r_2=R+R/2=3/2R`
Now, gravitational force , `F=(GMm)/(r^2)`
So, `(F_1)/(F_2)=((r_2)/(r_1))^2`
`therefore F_2=F_1*((r_1)/(r_2))^2=63xx((R)/(3//2R))^2=63xx4/9=28 N`