[填空题]
An atomic nucleus at rest decays rad1pp (sa6:/tkw2t acgm iov(o9 dg* 7ev2qop,pykactively into an alpha particle and a smaller nucleus. What will be the speed of this recoiling nucleus if the speed of the 7 d 2oqg,p9v (*opkyvealpha 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