The radius of earth is about `6400Km` and that of mars is about `3200 km` The mass of the earth is about `10`times the mass of mars. An object weight `200N` on earth 's surface, then its weight on the surface of mars will be:

Explanation

Let `M, R` be the mass and radius of earth and `M', R'` be the mass and radius of mars.
If `g, g'` be the acceleration due to gravity on the surface of earth and mars respectively, then
`g = (GM)/(R^(2))` and `g' = (GM')/(R'^(2))`
If `m` is the mass of the body, then weight of body on earth is
`W = mg = (GM m)/(R^(2)) = 100 N` ..(i)
`W = (GM m)/((6.4 xx 10^(6))^(2)) = 100` ..(i)
Weight of body on mars
`W' = mg' = (GM' m)/(R^(12)) = (G xx (M//10) xxm)/((3.2 xx 10^(6))^(2))`
`(W')/(W) = (4)/(10)` or `W' = (4)/(10) W = (4)/(10) xx 100 = 40 N`