The weight of a body on the surface of the earth is 100N . The...

The acceleration due to gravity changes as one goes to a height from the surface of the earth. Let the new acceleration due to gravity be $g '$. The formula for acceleration due to gravity at a height is given by $g ' = \dfrac{g{R}^{2}}{{\left(R + h\right)}^{2}}$

The weight of the body on surface is $W = mg = 100N$

The weight at the given height is $W = mg '$.

$⇒ W ' = 100 \times \dfrac{{R}^{2}}{{\left(R + \dfrac{R}{4}\right)}^{2}} ⇒ W ' = 100 \times \dfrac{{R}^{2}}{\dfrac{25{R}^{2}}{16}} = 64N$