Answer:
at the top
Explanation:
Potential energy is the stored energy, mechanical energy,
or energy possessed by by virtue of the position of an object.an example of potential energy is the energy that a ball possesses by virtue of its sitting at the top of the stairs it being about to roll down the stairs.
Answer: When enough __energy__ is added to the substance, the solid reaches its _melting_ point and becomes a liquid
Explanation: since energy is being added the substance changes phase into a liquid .
Okay, haven't done physics in years, let's see if I remember this.
So Coulomb's Law states that

so if we double the charge on

and double the distance to

we plug these into the equation to find
<span>

</span>
So we see the new force is exactly 1/2 of the old force so your answer should be

if I can remember my physics correctly.
I would say 150 joules, i don't know if its right though check