Answer:
To find out what water is made of, it helps to look at its chemical formula, which is H2O. This basically tells us that the water molecule is composed of two elements: hydrogen and oxygen or, more precisely, two hydrogen atoms (H2) and one oxygen atom (O).
Explanation:
It is because change in the Mass of the object balances the change in the Volume of the object equally...........
The woman weighs 100N now.
Explanation:
Given:
F is given as 400N
one full additional earth radius formed
To Find:
Weight of the woman=?
Solution:
We know that gravitational force is inversely proportional to the square of radius.

where
is the gravitational force
is the radius square
So when radius is doubled, the force becomes one fourth of the original.
Therefore 
Using the formula F=ma
500N=50kg (a)
a= 10 m/s^2