题目

Take care of your spine（脊柱）The spine stands at the center of your health, providing your body with structure and support. It also contains your spine cord, a massive collection of nerves conveying electric signals from the rest of your body to your brain【1】Maintaining good posture( 姿势) is one of the most important things you can do to keep your spine healthy. Proper posture means standing or sitting while keeping your spine straight, except for its natural curves. Posture comes into play even when you are asleep. Sleeping on your side puts less stress on your spine than most ot一把雨伞的半径为r，且高出水平地面h．当雨伞以角速度ω旋转时，雨点自伞的边缘甩出，在地面上形成一圆圈，则此圆圈的半径为多少？