1. The problem statement, all variables and given/known data An astronaut in his space suit and with a propulsion unit (empty of its gas propellant) strapped to his back has a mass of 143 kg. During a space-walk, the unit, which has been filled with propellant gas, ejects some gas with a velocity of +30.9 m/s. As a result, the astronaut recoils with a velocity of -0.265 m/s. After the gas is ejected, the mass of the astronaut (now wearing a partially empty propulsion unit) is 167 kg. What percentage of the gas propellant in the completely filled propulsion unit was depleted? 2. Relevant equations Pfinal = Pinitial P = mv 3. The attempt at a solution -.265(astronaut + gas) = 30.9 (gas) -.265(143 + x) = 30.9x -37.846 -.265x = 30.9x 31.165x = -37.846 x = 1.214 kg This can't be right, because the total after expulsion is 167 kg, meaning there is at least 24 kg of gas in the tank. Any ideas?