Hi good people!,

kindly just check if I did this correctly?

Make r the subject:

\(F=K{Q1Q2 \over r^2}\)

I did this:

devide by K:

\({F \over K}={Q1Q2 \over \ r^2}\)

Multiply by r^2

\({Fr^2 \over K}=Q1Q2\)

Multiply by K

\(Fr^2=K(Q1Q2)\)

Devide by F

\(r^2={K(Q1Q2) \over F}\)

\(r= \sqrt{K({Q1Q2} \over F}\)

Thanx for the time!

Guest Feb 21, 2018

#1**+3 **

Your method is correct, but you can do it without dividing by K and then multiplying by K :

\(F\,=\,K\cdot\frac{Q_1Q_2}{r^2} \\~\\ F\,=\,\frac{K(Q_1Q_2)}{r^2}\)

Multiply both sides of the equation by r^{2}

\(Fr^2\,=\,K(Q_1Q_2)\)

Divide both sides of the equation by F .

\(r^2\,=\,\frac{K(Q_1Q_2)}{F} \)

If we need to include both solutions for r , then we need to take the positive and negative square root of both sides.

\(r\,=\,\pm\sqrt{\frac{K(Q_1Q_2)}{F}}\)

.hectictar Feb 21, 2018

#1**+3 **

Best Answer

Your method is correct, but you can do it without dividing by K and then multiplying by K :

\(F\,=\,K\cdot\frac{Q_1Q_2}{r^2} \\~\\ F\,=\,\frac{K(Q_1Q_2)}{r^2}\)

Multiply both sides of the equation by r^{2}

\(Fr^2\,=\,K(Q_1Q_2)\)

Divide both sides of the equation by F .

\(r^2\,=\,\frac{K(Q_1Q_2)}{F} \)

If we need to include both solutions for r , then we need to take the positive and negative square root of both sides.

\(r\,=\,\pm\sqrt{\frac{K(Q_1Q_2)}{F}}\)

hectictar Feb 21, 2018