What Is the Time for a Particle to Reach the Force Center from Distance d?

[mushupork5]

I can't seem to figure this one out.
A particle at rest is attracted to a center of force by the relation
F=-mk^2/x^3
what is the time it takes for the particle to get to the force center from a distance d in terms of d and k?

I can't seem to find any equations that will help me out on this one. Thanks PF

 

[Lee]

I would like to point you towards Newtons second Law.

 

[mushupork5]

the clue i was given is that energy is constant and equal to the potential energy at the initial position

 

[mushupork5]

figured it out, thanks though