this is james bond

In[113]:=
Clear["Global`*"]

In[114]:=
m=85;T=2.1;g=9.8;

In[115]:=
sol[v0_]:=NDSolve[{m y''[t]\[Equal]-1.1y[t]^3+m g,y[0]\[Equal]0,y'[0]\[Equal]
v0},y,{t,0,T}]

In[116]:=
sol[6]

Out[116]=
{{y\[Rule]InterpolatingFunction[{{0.,2.1}},<>]}}

In[118]:=
yend[v0_]:=y[T]/.sol[v0][[1]]

In[119]:=
FindRoot[yend[v0]\[Equal]12,{v0,5,7}]

Out[119]=
{v0\[Rule]4.98583}

In[120]:=
sol[4.985825509081739`]

Out[120]=
{{y\[Rule]InterpolatingFunction[{{0.,2.1}},<>]}}