Physics help! -What is the electric potential at a point midway between the charges?

Two point charges Q1 = +4.50 nC and Q2 = -3.00 nC are separated by 37.0 cm.

(a) What is the electric potential at a point midway between the charges?

_______ V

(b) What is the potential energy of the pair of charges?

_______ J

What is the significance of the algebraic sign of your answer?

1.) Negative work must be done to separate the charges.

or

2.) Positive work must be done to separate the charges.

(a) Electric potential= (1/4pi-epsilon nought)*(Q1/r1 + Q2/r2)

Midway so I assumed that the distance is .185 meters

Then, 9X10^9 Nm^2/C^2 (4.5X10^-9 C /0.185m + (-3.0X10^-9C/0.185m))

9X10^9 Nm^2/C^2 (1.5X10^-9/.185m)

answer: 72.97 V or 73 Volts

Potential Energy: -3.28X10^-25 J, formula is k=9X10^9 times (Q1Q2 all over distance(.37m))

if potential energy is negative like the one i got, it means that negative work must be done to assemble the charges and positive work must be done to separate them. if in case you got a positive potential energy it means that positive work must be done to assemble the charges and negative work must be done to separate them :) Hope i did it right, this is our lesson this past few days, and i'm also having a hard time understanding it ;)

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