[填空题]
A rocket of total mass 3180 kg is traveling ink9x3vgh/fqe wx 15 dj-s yqi+ y;ftt,* outer space with a velocity of 115m/s To alter its co s;y +tifqty,*urse by 35.0 $^{\circ} $, its rockets can be fired briefly in a direction perpendicular to its original motion. If the rocket gases are expelled at a speed of 1750m/s how much mass must be expelled? kg
