A particle of charge q and mass m is subjected to an electric field E… | JEE Main 2020 (4 Sep, Shift 2)

Q35JEE Main 2020 · 4 SEP · SHIFT 2Difficult

Motion of Charges in an Electric Field

A particle of charge q and mass m is subjected to an electric field

E = E0 (1 – $a$ x2) in the x-direction, where $a$ and E0 are constants. Initially the particle was at rest at x = 0. Other than the initial position the kinetic energy of the particle becomes zero when the distance of the particle from the origin is:

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Answer: (c)

Work–energy: $KE = \int_0^x qE_0(1 - ax^2)\,dx = qE_0\left(x - \frac{ax^3}{3}\right)$
$KE = 0$ again when $1 - \frac{ax^2}{3} = 0$ .
$x = \sqrt{\frac{3}{a}}$
So the answer is (c).

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Motion of Charges in an Electric Field question from JEE Main 2020 (4 Sep, Shift 2)

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