[填空题]
A rocket of total mass 3180 kg is traveling in o*p1nkd 3x1 bvk y :vcmd)8fgm3uter sic5i a crvwi* 9y(o*+apace with a velocity of 115m/s To alter its course by 3va oi+(c 5r*yaw* i9ci5.0 $^{\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