Question

a planet has twice the mass of the earth and of identical size. what will be the hight above the surface of the planet where it's acceleration due to gravity reduces by 36% of its value on the surface?
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Answer 1

Answer:

we know acceleration due to gravity on surface of earth is g=GM÷ r^2 where r is the radius of earth. since mass is 2M of the planet acceleration due to gravity on surfave of planet is g'= G2M÷r^2, =2g.we know at a height h above surface g"=g'(1-(2 h÷ r)) . on the planet g" = g'-0.36g'=0.64 g' =0.64×2g=1.28g. 1.28g=2g(1-(2h÷r)).0.64=(1-(2h÷6400000)). 0.36=2h÷ 6400000.(0.36×6400000) = 2h.h=1152000 metres. Hope this is the right answer