[填空题]
A 25.0-g bullet strikes a 0.6 d 6t,a*nifd/ mdc f;*xc) wehv4s83sb00-kg b:(ph5 l y(jnp:8dehkq4 3o chmlock attached to a fixed horizontal spring whose spring stif38ypcn(de l:(h4hhmjp5 k:qo fness constant is $ 7.7\times10^{3 }$ N/m The block is set into vibration with an amplitude of 21.5 cm. What was the speed of the bullet before impact if the bullet and block move together after impact? m/s