题干

如图所示,让钢球从斜面上由静止滚下,打到一个小木块上,能将木块撞出一段距离.放在同一水平面上相同位置的木块.被撞得越远,表示钢球的动能越大.现用质量不同的钢球从同一高度滚下,看哪次木块被推得远.回答以下问题.

上一题 下一题 0.0难度 选择题 更新时间:2011-02-25 03:32:19

答案(点此获取答案解析)

同类题3

阅读理解

    It was Mother's Day morning last year and I was doing my shopping at our local supermarket with my five-year-old son, Teayson. As we were leaving, we found that only minutes earlier an elderly woman had fallen over at the entrance and had hit her bead on the concrete. Her husband was with her, but there was blood everywhere and the woman was embarrassed and clearly in shock.

    Walking towards the scene, Tenyson became very upset about what had happened to the couple. Ile said to me. “Mums it's not much fun falling over in front of everyone.”

    At the front of the supermarket a charity group had set up a stand selling cooked sausages and flowers to raise funds. Tenyson suggested that we should boy the lady a flower. “It will make her feel better,” he said. I was amazed that he'd come up such a sweet idea. So we went over to the flower seller and asked her if we could buy a flower for the lady to cheer her up. “Just take it,” she replied. “I can't take your money for such a wonderful gesture.”

    By now paramedics(救援人员) had arrived, and were attending the injured woman. As we walked up to her, my son became intimidated by all the blood and medical equipment. He said he was just too scared to go up to her.

    Instead I gave the flower to the woman's husband and told him. “My son was very upset for your wife and wanted to give her this flower to make her feel better.”

    At that, the old man started crying and said, “Thank you so much, you have a wonderful son, Happy Mother's Day to you.”

The man then bent down and gave his wife the flower, telling her who it was from. Though badly hurt and shaken, the old lady looked up at Tenyson with love in her eyes and gave him a little smile.