A body weighs 72 N on the surface of the earth. What is the gravitational force on it due to earth at a height equal to half the radius of the earth from the surface

Options

A. 16N
B. 28N
C. 32N
D. 72N

Answer

C

Explanation

Weight of body on the surface of the earth = mg = 72 N Acceleration due to gravity at height h is
`g_(n)=(gR_(E)^(2))/((R_(E)+h)^(2))=(gR_(E)^(2))/((R_(E)+(R_(E))/(2))^(2))=(4)/(9)g" "(becauseh=(R_(E))/(2))`
Gravitational force on body at height h is
`f=mg_(h)=mxx(4)/(9)g=(4)/(9)xxmg=(4)/(9)xx72N=32N`.