Differential equation of motion

[Lozzakw]

Homework Statement

Find the maximal ground reaction force for the limiting case where the speed at initial contact is equal 0 (Vo=0) expressing it as a mulitple of the body weight (mg)
ω = √k/m

Homework Equations

Y1(t) = A sinωt + B cos ωt + g/ω^2

The Attempt at a Solution

I know A and B are constants based on the initial conditions but as y=0 and Vo= 0 and there is no x componant - what other initial conditions can I use?

 

[haruspex]

Please quote the whole question.