JEE Main · 2022 · 27 Jun 2022 · Shift 2 · Electrostatics

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Three identical charged balls each of charge 2 C are suspended from a common point P by silk threads of 2 m each (as shown in figure). They form an equilateral triangle of side 1 m .

The ratio of net force on a charged ball to the force between any two charged balls will be :

(A) $1 : 1$
(B) $1 : 4$
(C) $3 : 2$
(D) $3 : 1$ ✓ Correct

Answer: (D)

Solution

Force between any two charges:

F = \frac{k ( 2 ) ( 2 )}{1 ^{2}} = 4 k

. Each ball experiences forces from the other two balls at 60° to each other. The net force magnitude is

F_{net} = 2 F cos (30°) = 2 F \times \frac{3}{2} = F 3

. Therefore

\frac{F _{net}}{F} = 3 : 1

JEE Main · 2022 · 27 Jun 2022 · Shift 2 · Single correct option

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