False.
Theories are hypotheses that have been shown to accurately and predictably explain results obtained through repeated experimentation, to the point where the hypothesis can be assumed to be true. Then, such a hypothesis would be considered a theory.
This can be solved using momentum balance, since momentum is conserved, the momentum at point 1 is equal to the momentum of point 2. momentum = mass x velocity
m1v1 = m2v2
(0.03kg x 900 m/s ) = 320(v2)
v2 = 27 / 320
v2 = 0.084 m/s is the speed of the astronaut
In object in motion stays in motion; speed