GM=6.674*5.972*10^13
r'(t,r,v)=v
v'(t,r,v)=-1*GM/r^2
r0=6.37*10^6
v0=slider(1000,20000,1000)
t0=0
tFinal=900
NSolveODE({r',v'},t0,{r0,v0},tFinal)
rMin=Min(y(First(numericalIntegral1,Length(numericalIntegral1))))
rMax=Max(y(First(numericalIntegral1,Length(numericalIntegral1))))
ZoomIn(t0,rMin,tFinal,rMax)