• # question_answer Three charges $1\mu C,\,\,1\mu C$ and $2\mu C$ are kept at the vertices $A,\,\,B$ and $C$ of an equilateral triangle $ABC$ of $10cm$ side, respectively. The resultant force on the charge at $C$ is A) $0.9N$                               B) $1.8N$ C) $2.72N$                             D) $3.6N$

Correct Answer: D

Solution :

The situation is shown in figure. Force on $C$ due to $A$                 ${{F}_{AC}}=\frac{1}{4\pi {{\varepsilon }_{0}}}\frac{{{q}_{A}}{{q}_{C}}}{r_{AC}^{2}}$                 $=\frac{9\times {{10}^{9}}\times 1\times 2\times {{10}^{-12}}}{{{(0.1)}^{2}}}=1.8N$ Similarly,              ${{F}_{BC}}=1.8N$ Hence, net force on                 $C={{F}_{AC}}+{{F}_{BC}}=3.6N$

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