A particle of mass 0.5 kg moves on the positive $x$-axis under the action of a variable force $\large\frac{40}{x^2}$ newtons,directed away from origin..The particle passes through a point 2 metres from origin,with velocity $8ms^{-1}$ away from origin. Its experiences a constant resistance force of 6 newtons. Find the speed of the particle when it is 5 metres from origin.

Question

$\begin{array}{1 1}\sqrt{40}ms^{-1}\\\sqrt{30}ms^{-1}\\\sqrt{15}ms^{-1}\\\sqrt{13}ms^{-1}\end{array} $