[填空题]
An atomic nucleus at rb,okl se6b sga/mhj6:fof/u 4-/dt,,qmo.kpestf2f f; ex-pj lof+f87nx/ mk*u decays radioactively into an alpha particle and a smaller nucleus. Whauf*l o +2p8nkj;-ef/7f f xfmxt will be the speed of this recoiling nucleus if the speed of the alpha particle is $ 3.8\times10^{5 }$m/s Assume the recoiling nucleus has a mass 57 times greater than that of the alpha particle. m/s
