Answer: The recoil speed is - 8.9604.[tex]10^{4}[/tex] m/s.
Explanation: According to the Third Law of Newton, every action has an oppsite and equal reaction, and the Second Law of Newton, Force=mass·acceleration. Acceleration is a variation in velocity by any given time, so Force = mass·velocity·time.
Combining the two laws, there is : m1·v1 = - m2·v2. This is the Law of Conservation of Momentum.
Substituting and calculating:
v2 = - ([tex]\frac{m1}{m2}[/tex]) · v1
v2 = - [tex]\frac{6.64.10^{-27} }{3.88.10^{-25} }[/tex] · 5.24.[tex]10^{6}[/tex]
v2 = - 8.9604.[tex]10^{4}[/tex]
The recoil speed of the thorium nucleus is - 8.9604.[tex]10^{4}[/tex]m/s.