Answer:

Explanation:
The equation for centripetal acceleration is

Where v is the tangential velocity and r the radius of the orbit.
To calculate v we notice that the moon travels the circumference of the orbit
in a time T, so we have

Putting all together:

And since the radius r is d/2, where d is the diameter of the moon's orbit, we can write the formula asked:

Answer:
The displacements are not equal. While their direction is the same, their length (i.e., distance or magnitude) is not. A is longer than B.
Explanation:
correct on e2020- sample respnse
To solve this problem we will use the equilibrium conditions in the Electrostatic Forces. In turn, we will use the concept formulated from Coulomb's laws to determine the intensity of the Forces and make the respective considerations.
Our values for the two charges are:


As a general consideration we will start by determining that they are at a unit distance (1) separated from each other. And considering that both are negative charges, they will be subjected to repulsive force. Said equilibrium compensation will be achieved only by placing a third force between the two.
Let the third charge be
is placed at a distance x from 

The force on
due to
is

The condition of equilibrium is



from 
To find the magnitude of
we use 


The magnitude of the third charge must be 0.43 the first charge 
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