Question

Two charges, each equal to q, are kept at `x=-a` and `x=a` on the x-axis. A particle of mass m and charge `q_0=q/2` is placed at the origin. If charge `q_0` is given a small displacement `(ylt lt a)` along the y-axis, the net force acting on the particle is proportional to
A. (a) y
B. (b) `-y`
C. (c) `1/y`
D. (d) `-1/y`

Answer 1

Correct Answer - A
`impliesF_(n et)=2F cos theta`
`F_(n et)=(2kq(q/2))/((sqrt(y^2+a^2))^2)*(y)/(sqrt(y^2+a^2))`
`F_(n et)=(2kq(q/2)y)/((y^2+a^2)^(3//2))implies(kq^2y)/(a^3)`
So, `Fpropy`