Question

Find the value of the acceleration due to gravity at a height of 12,800 km from the surface of the earth Earth's radius = 6400 km. (ii) State Newton's law of gravitation and write the mathematical equation describing itCBSE Class IX Science SA 2 (3 Marks)

Answer 1

1) use formula

g'=g/(1+h/r)^2
=g/(1+12800/6400)^2
=g/(1+2)^2
=g/9 m/sec^2
hence acceleration due to gravity at 12800km height is g/9 m/sec^2

ii) Newton law of gravitation :-sir issac Newton say that gravitational force must be exist between two body present in the universe which is directly proportional to product of mass of the bodies and inversely proportional to square of separation between two bodies .e.g.
let M and m are two bodies and r is the separation between these bodies
according to Newton law ,
F=GMm/r^2
where G is known as gravitational constant .