`m_B` =35 g= 0.035 kg
`v'_B` =875 m/s
Since the firing is instantaneous, momentum shall be conserved for the firing process. i.e.
Sinec `v_A` and `v_B` are both zero, the above relation reduces to,
`=-0.365 ` m/s
Thus, the astronaut recoils in a direction opposite to that of the moving gas with a velocity of 0.365 m/s.