题目

在“验证机械能守恒定律”的实验中，质量为m的重锤从高处由静止开始下落，重锤上拖着的纸带通过打点计时器所打出一系列的点，对纸带上的点迹进行测量就可以验证机械能守恒定律。 （1）如图所示，选取纸带打出的五个连续点A、B、C、D、E，测出A点距起始点O的距离为S0，其余如图，使用电源的频率为f（频率为周期的倒数），则打C点时重锺的速度为      ▲       ，打点计时器在打C点时重锤的动能为    ▲      ，打点计时器在打O点和CStay on the brighter side of life One very important component of optimism is gratitude or feeling grateful．In fact, there is a strong connection between a grateful attitude and a heightened sense of well-being．Appreciate all the positives in your life by starting a gratitude journal in order to remember what you’re grateful for．1. Feeling down？Instead of feeling sorry for yourself waiting for the universe to throw you a bone, try acting like you’re happy—even if you aren’t．A sincere smile and a forced smile will cause the same chemical reactions in your brain, so you can actually fool your mind into feeling better by making it react chemically as if things were going well．2. Reassure yourself that everything is good— even if you don’t feel it． “3.If you’re stuck in traffic, then everything else must be going horribly too,” says Anne Parker, a wellness counselor．By blowing negative events out of proportion, you’re setting yourself up for feeling down all day．Instead, acknowledge that you’re stuck in traffic, but also bring to mind something good, like the beautiful scenery outside the window．That way, you’ll get in the habit of forbidding negative circumstances from blanketing your whole day． Swearing to lose 20 pounds or to run a marathon seems like goals leading to happiness, but they take time to achieve．4.You may even end up admitting that you have been defeated．However, if you focus on the small milestones that occur along the way, you will feel positive about your progress, which will give you the strength to keep going． 5. Try making someone else’s day better．A report by United Healthcare and Volunteer Match found that volunteers are 72% more likely to characterize themselves as optimistic compared with non-volunteers．Plus, 89% of volunteers say that volunteering has improved their sense of well-being, and 92% say that it enriches their sense of purpose in life． A．Try to help someone in need． B．Want to give your attitude a lift？ C．People tend to think in an either-or way． D．Act in an optimistic way—smile, laugh, tell a joke． E．You’ll fail to appreciate more important things in your life． F．By focusing on not having accomplished them yet, you will start to feel down on yourself． G．By remembering the pleasant things in your life, you can actually turn a negative attitude around．