#v0=state[1]
#a=-k*state[0]
#g1=state[1]
#g2=(L0+state[0])*state[3]*state[3]-(k/m)*state[0]+g*cos(state[2])
#g3=state[3]
#g4=-1/(state[0]+L0)*g*sin(state[2])+2*state[1]*state[3]

rdot = state[0] #Vr
phidot = state[1] #Vphi
vrdot = ((-state[2] * g) - (state[3] * r * sqrt(phidot)))/(state[3] + state[2])
vphidot = (2*rdot * phidot)/r
return array([rdot,phidot,vrdot,vphidot])