A uniform electric field of strength E exists in region. A electron enters a point A with velocity v as shown. It moves through the electric field and reaches at point B. Velocity particle at B is `2v` at `30^@` with x-axis . Then A. electric field `E=(3mv^2)/(2ea) hati`B. rate of doing work doen by electric field ast B is `(3mv^2)/(2ea)`C. Bota a and b are correctD. both a and b are wrong

A uniform electric field of strength E exists in region. A electron en

1.	A uniform electric field of strength E exists in region. A electron enters a point A with velocity v as shown. It moves through the electric field and reaches at point B. Velocity particle at B is `2v` at `30^@` with x-axis . Then A. electric field `E=(3mv^2)/(2ea) hati`B. rate of doing work doen by electric field ast B is `(3mv^2)/(2ea)`C. Bota a and b are correctD. both a and b are wrong
Answer» Correct Answer - A `(v_A)y=vimplies(v_B)_y=2vsin30^@v` Since y-component of velocity remains unchanged. Hence electric field is along `(-hati)` direction. Work done by electrostatic force in moving from A and B =change in its kinetic energy `:. (eE)(2a-a)1/2m(4v^2-v^2)` `E=(mv^2)/(2ea)` `or E=-(3mv^2)/(2ea)hati` Rate of doing work done =power `=Fvcostheta` `((3mv^2)/(2ea))^2(e)(2v)cos30^@` `=3sqrt3/2(mv^2)/a`

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