The bullet moves vertically: h= 12gt2? ②

Rotation of cylinder: 2π? n=ωt③

Vertical component motion of cylinder: h=vt④

Simultaneous solution: t=2vg

v′= Rgv

ω=nπgv(n= 1.2…)

So the answer is: Rgv, ω = n π gv (n = 1.2 ...).