CBSE Class 12-science Answered

Each pith ball will be 0.2/2 = 0.1 m from the vertical centre line.

The vertical component of tension in the string is equal to the weight of a pith ball.

T_y = Tsinθ, where θ is the angle made by string with horizontal.

Hypotenuse = Length of the string = 0.5 m

Adjacent side = 0.1 m

Opposite side = (0.5²-0.1²)^1/2 = 0.49

T_y = Tsinθ = W = 10^-3x10 N

T = (10^-3x10)/(0.49/0.5) = 10.20x10^-3

The horizontal component of tension is the electrostatic force of repulsion,

kq²/r² = Tx = Tcosθ = 10.20x10^-3 (0.1/0.5)

q² = (10.20x10^-3 )(0.1/0.5)(0.2²)/(9x10⁹) = 0.009x10^-12

q = 0.09 x 10^-6 C

q = 90 nC.

Regards,

Team,

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