[填空题]
An alpha particle (whicy n9s (rc:zs cd/o1.,z ,jkpxch bqi3 tvy ( vqc217(jvnez1qcs3a7t 0gis a helium nucleus, $Q=+2e$, $m\,=\,6.64\times10^{-27 }\,kg$) is emitted in a radioactive decay with $_{KE}$ = $5.53MeV$ What is its speed? $ \times10^{7}\,m/s$
