一、填充題
1. A fully fueled rocket has a mass of 21,000 kg, of which 15,000 kg is fuel. The burned fuel is spewed out the rear at a rate R = 150 kg/s with a speed of 3000 m/s relative to the rocket. If the rocket is fired vertically upward, calculate: (a) the thrust of the rocket (1)______, and (b) its final velocity at burnout (fuel is fully consumed): (2)______. Ignore the air resistance. [Hint: 1^st rocket eq.: R_vrel = Ma; 2^nd rocket eq.: v_f − v_i = v_rel ln(M_i/M_f) − gt, where g is considered as a constant value and t is the time for fuel burnout.].