题干

小明在老师的指导下用小球和弹性很好的轻质橡皮筋等器材进行了如下实验与探究:让一系于橡皮筋一端的小球从某悬挂点O的正下方P点由静止释放如图甲所示,整个下落过程中,橡皮筋所受弹力F与小球下落高度h的关系如图乙所示;小球下落的速度v与下落高度h的关系如图丙所示。已知该轻质橡皮筋每受到0.1N的拉力就伸长1cm,经测量小球从P点下落到A、B、C三点的距离分别为:ha=0.4m,hb=0.5m,hc=0.7m。(不计空气阻力).

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 We all know that exercise is good for your health. But some kinds of exercise may be better than others. Running, for example, may help to protect against heart disease and other health problems. Running may also help you live longer.

 Recently, researchers studied more than 55,000 adults. About a quarter of the adults have a good habit of running. The study found these runners were much healthier than non-runners. In fact, the runners lived, on average(平均), three years longer than the non-runners.

 Running may be good exercise, but it can be difficult on the body. Here are commonly shared ideas among fitness experts(健身专家) to lower the risk of injury(受伤) for people who are new to running.

⊙Take it easy.

 Do not run too much, too soon or too fast. Most people get running injuries when they push themselves too hard. The body needs time to get used to increases in distance(里程) or speed.

⊙ Get good running shoes.

 There is no single best shoe for every runner. You should find the shoe that offers the best fit and support for your feet. More importantly, you should have a new pair of shoes every 500 to 800 kilometers.

⊙Take good notes.

 Take time after each run to write down notes about what you did and how you felt. Look for things that happen again and again. For example, you may find that your knees hurt when you run sometimes. But perhaps you feel great when you have a rest between running days. These notes will help you make the best plan for running.