A rocket accelerates straight up by ejecting gas downwards. In a small time interval Δt, it ejects a gas of mass Δm at a relative speed u. calculate KE of the entire system at t + Δt and t and show that the device that ejects gas does work = (1/2)Δmu^2 in this time interval

Q: A rocket accelerates straight up by ejecting gas downwards. In a small time interval Δt, it ejects a gas of mass Δm at a relative speed u. calculate KE of the entire system at t + Δt and t and show that the device that ejects gas does work = (1/2)Δmu^2 in this time interval (negative gravity)