题干

探究力对原来静止的物体做的功与物体获得的速度变化的关系,实验装置如图所示,实验主要过程如下:

⑴设法让橡皮筋对小车做的功分别为W、2W、3W

⑵分析打点计时器打出的纸带,求出小车的速度v1、v2、v3…;

⑶作出W﹣v草图;

⑷分析W﹣v图象,如果W﹣v图象是一条直线,表明w∝v;如果不是直线,可考虑是否存在w∝v2、w∝v3等关系.

以下关于该实验的说法中有一项不正确,它是       

A:本实验设法让橡皮筋对小车做的功分别为W、2W、3W,所采用的方法是选用同样的橡皮筋,并在每次实验中使橡皮筋拉伸的长度保持一致,当用1条橡皮筋进行实验时,橡皮筋对小车做的功为W,用2条、3条…橡皮筋并在一起进行第2次、第3次…实验时,橡皮筋对小车做的功分别是2W、3W.

B:小车运动中会受到阻力,补偿的方法,可以使木板适当倾斜.

C:某同学在一次实验中,得到一条记录纸带,纸带上打出的点,两端密、中间疏,出现这种情况的原因,可能是没有使木板倾斜或倾角太小.

D:根据记录纸带上打出的点,求小车获得的速度的方法,是以纸带上第一点到最后一点的距离来进行计算.

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D

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The Diet Zone: A Dangerous Place

    Diet Coke ,diet Pepsi, diet pills, no-fat diet, vegetable diet…We are surrounded by the word “diet” everywhere we look and listen. We have so easily been attracted by the promise and potential of diet products that we have stopped thinking about what diet products are doing to us. We are paying for products that harm us psychologically and physically.

    Diet products significantly weaken us psychologically. On one level, we are not allowing our brain to admit that our weight problems lie not in actually losing the weight, but in controlling the consumption of fatty, high-calorie, unhealthy foods. Diet products allow us to jump over the thinking stage and go straight for the scale instead. All we have to do is to swallow or recognize the word “diet” in food labels.

    On another level, diet products have greater psychological effects. Every time we have a zero-calorie drink,we are telling ourselves without our awareness that we don't have to work to get results. Diet products make people believe that gain comes without pain, and that life can be without resistance and struggle.

    The danger of diet products lees not only in the psychological effects they have on us, but also in the physical harm that they cause. Diet foods can indirectly harm our bodies because consuming them instead of healthy foods means we are preventing our bodies from having basic nutrients. Diet foods and diet pills contain zero calorie only because the diet industry has created chemicals to produce these wonder products. Diet products my not be nutritional,and the chemicals that go into diet products are potentially dangerous.

    Now that we are aware of the effects that diet products have on us, it is time to seriously think about buying them. Losing weight lies in the power of minds, not in the power of chemicals. Once we realize this, we will be much better able to resist diet products, and therefore prevent the psychological harm that comes from using them.

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