Electric potential midway between 2 charges

[kbyws37]

Charges of −12.0 nC and −21.0 nC are separated by 0.700 m. What is the potential midway between the two charges?


I used the equation V = kq / r for each charge
and then added both V's. But I got it wrong. (the correct answer should be -847 V)
So...


V1 = (8.9x10^9)(-12 x 10^-9) / 0.7 = -152.6
V2 = (8.9x10^9)(-21 x 10^-9) / 0.7 = -267

V1 + V2 = -152.6 + (-267) = -420

What am i doing wrong?

 

[denverdoc]

maybe just algebra, the distance you need to use is the 1/2 way point of 0.35 see if that helps.

 

[m2003]

It appears that you may have made an error in your calculation for V2. The correct value for V2 should be -267.4 V, not -267 V. When you add this to V1, you get a total potential of -419.9 V, which is very close to the correct answer of -847 V. This small difference could be due to rounding errors or inaccuracies in the values used for the charges and distance. To ensure accuracy, it is important to use the exact values given in the question and use a calculator with enough significant figures. Additionally, double checking your calculations and units can help catch any mistakes.