Question

A
8) Three identical charges each of 2 uC are
placed at the vertices of a triangle ABC as
shown in the figure.
If AB + AC = 12 cm and AB. AC = 32 cm,
the potential energy of the charge at A is
(a) 1.53 J (b) 5.31 J
(C) 3.15 J
С -
B
(d) 1.35 J

Answer 1

Answer: (d) - 1.35

Explanation:

AB ∙ AC = 32cm2

∴ AB = (32/AC)

∴ [(32)/(AC)] + AC = 12

∴ 32 + AC2 – 12AC = 0

AC2 – 12AC + 32 = 0

AC = 4 cm, 8 cm Let AC = 4 cm

∴ AB = 8 cm

Potential energy point A = VA = kq1q2 [(1/AB) + (1/AC)] = 9 × 109 × 2 × 10–6 × 2 × 10–6[(1/4) + (1/8)] × 102 = 36 × 10–1 × (12/32) VA = 1.35J