A body weight 72 N moves from the surface of earth at a height half of the radius of the earth , then gravitational force exerted on it will be .......

Options

A. 72 N
B. 28 N
C. 10 N
D. 32 N

Answer

D

Explanation

`implies` Weight = Gravitational force
`:.W = (GM_em)/(R_e^2)" " :.72 = (GM_em)/(R_e^2)`
Now w = `=(GM_em)/((R_e+R_e/2))=(GM_em)/((3/2R_e)^2)=(GM_em)/(3/2Re)=4/9(GM_em)/(-R_e^2)`
`:. W. = 4/9 xxW`
`:. W = 4/9 xx 72 = 32 N`