free-fall velocity

例句：

1. 1. The spacecraftis designed to travel at a free-fall velocity of 2,000 miles per hour.
   这个宇宙飞船设计的速度是每小时2000英里的自由落体速度。
2. 2. The projectile will continue to move at its free-fall velocity for another 15 seconds.
   弹丸将继续以其自由落体速度移动另外15秒。
3. 3. The physics experiment measures the free-fall velocity of the object as it falls through the air.
   这个物理实验测量了物体在穿过空气时的自由落体速度。