游泳的基本姿势有哪些？
user
游泳的基本姿势主要包括四种：自由泳（爬泳）、蛙泳、仰泳和蝶泳。每种姿势有其独特的动作特点和技术要求，适用于不同的游泳需求和场合。自由泳速度最快，蛙泳和仰泳相对轻松，蝶泳则需要较强的爆发力和协调性。
assistant
列出联合国安理会的5个常任理事国。
user
联合国安理会的5个常任理事国是中国、美国、俄罗斯、英国和法国。这些国家拥有否决权，对安理会的决策有重要影响。
assistant
threw a ball into the air. How does the ball's velocity change as it goes up, reaches the top, and comes back down?
user
When a ball is thrown into the air, its velocity changes in the following way:

1. **Going Up:** As the ball moves upward, its velocity decreases due to the force of gravity acting downward. The ball slows down until it reaches its highest point.
2. **At the Top:** At the highest point, the ball's velocity is zero because it momentarily stops before changing direction.
3. **Coming Down:** As the ball descends, its velocity increases due to the force of gravity acting downward. The ball speeds up until it reaches the ground.

Throughout this motion, the acceleration due to gravity is constant at approximately 9.8 meters per second squared (m/s²) downward.
assistant