Question

A charge A of 25 $\mu$C is placed on the line between two charges B of 5 $\mu$C and C of 30 $\mu$C. The charge A is 0.05m from B and 0.1m from C. What is the force on A

• A. 1.125N
• B. 11.25N
• C. 1125N
• D. 225N

Answer 1

The correct option is D 225N

$F=F_B+F_C=9\times {10}^9[\frac{25\times 5\times {10}^{-12}}{5^2\times {10}^{-4}}-\frac{25\times 30\times {10}^{-12}}{{10}^{-2}}]$

$=9\times {10}^9\times {10}^{-12}[5\times {10}^4-25\times 30\times {10}^2]$

$=9[50-75]=-9\times 25=-225N$