• # question_answer Three forces acting on a body are shown in the figure. To have the resultant force only along the y-direction, the magnitude of the minimum additional force needed is A) $\frac{\sqrt{3}}{4}N$           B)  $\sqrt{3}\,N$ C)  0.5 N              D)  1.5N

Correct Answer: C

Solution :

Taking x-components, the total should be zero. $\frac{Q}{4\pi {{R}^{2}}}=\frac{q}{4\pi {{r}^{2}}}=\sigma$ $\therefore$ $V=\frac{1}{{{\varepsilon }_{0}}}\,[\sigma R+\sigma r]=\frac{\sigma }{{{\varepsilon }_{0}}}[R+r]$ This is the required force in x-direction.

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