an object weighs 10N on earth .what is the objects weight on a planet one tenth the earths mass and one half its radius?

Answer 1

Weight is mass m times acceleration due to gravity g, which is given by g=GMm/R^2 where M and R are mass & radius of Earth and G is Universal Gravitational Constant.
For new planet, g`=G(0.1Mm/(R/2)^2
=0.1GMm/R^2/4
=GMm(0.1x4)/R^2=0.4GMm/R^2
Hence g/g`=0.4, which means the weight on the new planet will be 10X0.4=4N.