题目

All over the world people enjoy sports. Sports help to keep people healthy, happy and help them to live longer. 36． They buy tickets or turn on their TVs to watch the games. Often they get very excited when “their” player or team wins. 37． Football, for example, has spread around the world. Swimming is popular in all countries near the sea or in those with many rivers. What fun it is to jump into a pool or lake, whether in China, Egypt or Italy! 38． Think how many people love to skate or ski in Japan, Norway or Canada. Some sports or games go back to thousands of years, like r 一个质量为0.3 kg的弹性小球，在光滑水平面上以6 m/s的速度垂直撞到墙上，碰撞后小球沿相反方向运动，反弹后的速度大小与碰撞前相同．则碰撞前后小球速度变化量的大小Δv和碰撞过程中墙对小球做功的大小W为 A．Δv＝0 B．Δv＝12 m/s C．W＝0 D．W＝10.8 J