A uranium nucleus 238U may stay in one piece for billions of years, but sooner or later it decays into an α particle of mass 6.64×10-27 kg and 234Th nucleus of mass 3.88 × 10-25 kg, and the decay process itself is extremely fast (it takes about 10-20 s). Suppose the uranium nucleus was at rest just before the decay. If the α particle is emitted at a speed of 1.74×107 m/s, what would be the recoil speed of the thorium nucleus?