# ABC  is a right angled triangle in which AB = 3 cm  and BC = 4 cm . And $\angle ABC=\pi l2.$ The three charges +15 , +12   and -20 e.s.u.  are placed respectively on A , B  and C . The force acting on B  is Option 1) $125\; \; dynes\;$ Option 2) $\; 35\; \; dynes\;$ Option 3) $\; 25\; \; dynes\;$ Option 4) $\; Zero$

V Vakul

As we learned

Principle of Super Position -

It states that total force acting on a given charge due to number of charges is the Vector sum of the individual force acting on that charge due to all the charges.

- wherein

Net force on     $BF_{net}=\sqrt{F_{A}^{2}+F_{C}^{2}}$

$\\*F_{A}=\frac{15\times 12}{(3)^{2}}=20\, dyne,\; F_{C}=\frac{12\times 20}{(4)^{2}}=15\, dyne\\*\Rightarrow F_{net}=\sqrt{F_{A}^{2}+F_{C}^{2}}=\sqrt{(20)^{2}+(15)^{2}}=25dyne$

Option 1)

$125\; \; dynes\;$

Option 2)

$\; 35\; \; dynes\;$

Option 3)

$\; 25\; \; dynes\;$

Option 4)

$\; Zero$

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