Answer:
E = 0 r <R₁
Explanation:
If we use Gauss's law
Ф = ∫ E. dA =
/ ε₀
in this case the charge is distributed throughout the spherical shell and as we are asked for the field for a radius smaller than the radius of the spherical shell, therefore, THERE ARE NO CHARGES INSIDE this surface.
Consequently by Gauss's law the electric field is ZERO
E = 0 r <R₁
The amount of gravitational potential energy acquired by the rock is equal to:

where
m is the mass of the rock
g is the gravitational acceleration

is the increase in height of the rock
Substituting the data of the problem, we find

So, Natalie gave 220.7 J of energy to the rock.
Answer:
If there are equal forces in both directions and there is no motion, the net force is 0 Newtons. This is because you'd be subtracting 100 from 100 which just equals 0.
The 2 means there are two phosphate ions in a molecule of magnesium phosphate.