Answer:
The magnitude of the electrostatic force decreases by a factor 9
Explanation:
The electrostatic force between two charges is given by:

where
k is the Coulomb's constant
q1 and q2 are the two charges
d is the distance between the two charges
We see that the magnitude of the force is inversely proportional to the square of the distance. If the distance is increased to 3d: d' = 3d, the new electrostatic force would be:

So, the electrostatic force decreases by a factor 9.
According to the information provided to define an average density, it is necessary to use the concepts related to mass calculation based on gravitational constants and radius, as well as the calculation of the volume of a sphere.
By definition we know that the mass of a body in this case of the earth is given as a function of

Where,
g= gravitational acceleration
G = Universal gravitational constant
r = radius (earth at this case)
All of this values we have,

Replacing at this equation we have that

The Volume of a Sphere is equal to

Therefore using the relation between mass, volume and density we have that

Refer to the diagram shown below
Given:
m = 2.8 kg, the mass of the bucket
a =3.1 m/s², the acceleration of the bucket
Therefore
W = 2.8*9.8 = 27.44 N, the weight of the bucket.
Let T = the tension in the rope.
From the free body diagram, the net force accelerating the bucket is
T - W = m*a
That is,
T = W + m*a
= 27.44 + 2.8*3.1 N
= 36.12 N
Answer: d. 36.1 N
Joules is work so you wood use the equation w=f(d)