Question

3. Radius of a planet is double than the radius of Earth and its mass is two times
than the mass of Earth. The weight of a 10 kg child on that planet will be-
(a) 5 kg
(b) 10 kg (c) 20 kg
(d) 40 kg​

Answer 1

Answer:

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mass of earth =m

moss of the new planet -2m

radius of earth =r

radius of new planet =2r

gravity acting on earth =G*m/r^2

gravity acting on new planet =G*2m/(2r)^2

=G*2m/4r^2

gravity of earth /gravity of the new planet (G*m/r^2)/(G*2m/4r^2)

=1/2

this means that the gravity acting on the new planet is twice the gravity acting on earth.

gravity acting on earth-9.8m/sec^2

gravity acting on new planet =2*9.8m/sec^2

=19.6m/sec^2

mass of child =10Kg

weight of child on new planet =mass of child gravity acting on new planet

=10kg*19.6m/sec^2

=196newton

OR

20kg

Explanation:

Option C 20kg is the right answer