d
(d)Potential energy of the particle \(U = k(1 - {e^{ - {x^2}}})\)
Force on particle\(F = \frac{{ - dU}}{{dx}} = - k[ - {e^{ - {x^2}}} \times ( - 2x)]\)
F\( = \, - 2kx{e^{ - {x^2}}}\)\( = - 2kx\left[ {1 - {x^2} + \frac{{{x^4}}}{{2\,!}} - ......} \right]\)
For small displacement \(F = - 2kx\)
\(⇒\) \(F(x) \propto - x\) i.e. motion is simple harmonic motion.