用塑料带抹布拖把擦玻璃,力气大些,会划裂玻璃吗?

10×3.14=31.4(cm)
31.4×2=62.8(cm)

(15*2*3.14)/2+15*2+1.8=78.9厘米

高分子材料指的是分子量很大的物质,塑料袋、橡皮筋、合成纤维属于这个范畴.
复合材料一般是加入了填料,不一定是分子量很大.钢筋混凝土应该是.

选C; D能分解,但污染环境.

录音的过程,就是磁头电磁铁,把带上的磁性材料进行磁化的过程
所以是用词性材料记录信息

(15*2*3.14)/2+15*2+1.8=78.9厘米

塑料袋不环保又花钱，自带环保购物袋，既省钱又可以造福自己的子孙后代，避免他们生活在白色污染中，何乐而不为? 请按一下采纳哦~O(∩_∩)O谢谢~

(15*2*3.14)/2+15*2+1.8=78.9厘米
70*3.14*140*60=1846320厘米=18463.2米=18.4632公里
圆周率我用的是3.14

不要怕,现在绝大部分装食品的塑料袋（包括保鲜袋）都是用聚乙烯制成的,这种材料在200摄氏度以下基本不会分解,也不会产生对人体有害的物质.
100摄氏度对大多数塑料来说都是安全的.

首先 N2在空气中比例很大 差不多80% 其次 应该是实验所需N2对纯度要求不大 所以制取很简约

装冷水的小塑料袋放入热水中会（下沉）,装热水的小塑料带放入冷水中会（浮起）,这说明热水比冷水（密度小）.

因为塑料化学成分都是高分子碳氢化合物,燃烧时加上氧气,经过燃烧的化学反应,自然就出现二氧化碳和水
比如：CH4（甲烷）+2O2（氧气）=CO2+2H2O

给我说一题

不用塑料袋、人境牵手.
善使花园净、疾净别离.
此句“牵手”“别离”
用了拟人的修辞手法.

　不如先想想什麼使鸡蛋破裂吧.
1.鸡蛋的速度
2.被撞击表面的硬度
3.鸡蛋外壳硬度低
对症下药:
1.给个降落伞减速
2.地面弄个软垫气垫,或鸡蛋外层包一个很软的保护套 (果冻或水也可能可以)
3.加硬外壳,给鸡蛋做个一寸厚的金属外壳,要原外壳与金属壳中间无空隙.

可以这样说,不过这中间还有好多的环节很过程

根据阿基米得原理物体所受浮力等于物体排开液体的重力.水放入水中浮力当然等于自己的重力,所以头发不受力!

Plastic and the Food Chain
Plastic Accumulates in Rivers, Oceans, Fish, and Us
作者：Sara E. Lewis
Sep 10, 2007
Plastic is man-made -- not easily broken down or reabsorbed by the environment. Clean-ups, consumer awareness, and alternative materials are needed.
News about plastic compounds in pet foods and toothpaste from China caught headlines in 2007. Afterwards, the USDA and FDA reported that they are investigating and testing a variety of imported food additives. Officials assured the public that, “The inspections are a precautionary measure to ensure the safety of products entering at U.S. ports of entry. There is no evidence to suggest products bound for the human food supply are contaminated.”
But the truth is that recent worries about plastics are the tip of the iceberg. Researchers have been concerned for some time about chemical compounds that make up plastic materials getting into the food supply. Plastic is the word we use to describe the many types of man-made or synthetic materials that become toys, containers, and more.
History of Plastic
Since the 1960s, plastics have become omnipresent. Many useful products that save time, reduce accidental injury, and improve quality of life are made from plastic. At the same time, there is no known organism that breaks down plastic in the environment, so every bit of plastic that has ever been made is very likely to be still with us. Estimates of how long it will take plastics to be reabsorbed by the environment range from 400 years to a much longer unit of geologic time.
History of Concern about Plastic in the Environment
By the 1980s, people worldwide began to notice the mess of plastic that was washing up on beaches and the harm it was doing to birds and animals that became tangled in fishing line and 6-pack rings. Initiatives like the Chesapeake Bay Foundation’s Clean the Bay Day program were organized to clean up debris on the beaches. While many participants saw such events as tidying up exercises, organizers have understood that they are also important initiatives aimed at keeping some plastic out of the food chain. According to the Chesapeake Bay Foundation, “shoreline litter is not just a public eyesore, it is harmful to wildlife, a source of toxic water pollution, and symptomatic of other, less visible forms of pollution entering local waterways.”
In England, University of Plymouth marine biologist Richard Thompson has combed the beaches since the 1980s and discovered dead birds with so many small pieces of plastic in their stomachs, probably scooped up mistakenely for food, that they likely died from starvation or blockage of the intestines.
Ten years ago, Captain Charles Moore of the Algalita Marine Research Foundation, on a trip across the Pacific Ocean after a sailing race, saw a patch of floating plastic debris in the North Pacific Gyre. This area of slow swirling current is said to be the size of the state of Texas. There are several such gyres where plastic floats around and around and is swept in and out by currents and tides. All the while, the mixed debris of such things as plastic bags, bottles, buckets, and toys is eroding into smaller and smaller pieces.
Both scientists and others have trawled to collect water samples and sort the debris to determine how many of the small particles in oceans and rivers are plastic. One-third and more of the samples contain tiny plastic pieces of the sort that birds and fish often see as their food. These researchers have found tiny particles of plastic embedded in the tissue of dead animals.
Plastics, Eating Fish, and Your Health
Captain Moore said, “The base of the food chain is being displaced by a non-digestible, non-nutritive component which is actually outweighing and outnumbering the natural food. That is our core issue.”
As the persistence of plastics in the environment becomes better understood, consumers are questioning the safety of eating fish. The Mayo Clinic answers that, “As good as fish are for your health, be aware of potential downsides. Some types of fish may contain significant amounts of contaminants, such as mercury, polychlorinated biphenyls, dioxins or other chemical pollutants. Fish acquire these toxins from pollutants in lakes, rivers and oceans.”
More research is needed to determine the ultimate consequence to humans of the accumulation of plastic that can concentrate toxic chemicals. But Neil Seldman of the Institute for Local Self Reliance has said that plastic is a bigger danger than global warming because it is killing the lowest common denominator in the food chain. The problem can only be eased when greater public awareness results in less use of plastic. Manufacturers who acknowledge the problem are looking into ways to create degradable plastics.
What You Can Do to Reduce Plastic in the Environment
In the meantime, the most effective way to limit the amount of plastic entering the food chain is beach cleaning. Also, consumers can look for alternative materials and avoid excessive use of single-use plastic bottles, containers, and packaging. Finally, by recycling, we can extend the useful life of plastic products.
((Permission to republish Plastic and the Food Chain in print or online must be granted by the author in writing. ))

1、塑料袋的抗戳穿强度大于笔尖的扎力,塑料袋瞬间变形,然后恢复正常.
2、塑料袋的抗戳穿强度小于笔尖的扎力,塑料袋被刺穿,水不会喷射,而是顺着孔沿着塑料袋外表溢流.

we should stop using the plastic
bags in order to protect our
environment.

塑料是高分子材料,广义上讲属于有机物,含大量的碳和氢元素,燃烧后当然会放出二氧化碳

As the society develops very fast,environment protection can be never ignored.Here I'd like to show my opinion toward this issue.We should learn to protect the environment in our daily life.Firstly,we must save water and electricity,as there are limited.Secondly,we mustn't throw litter around.Thirdly,we shall plant more trees.Trees can provide us fresh air and stop storms.Fourthly,we must refuse using plastic bags because the pollution is very serious and hard to eliminate.

塑料带伸长是因为材料在拉伸应力下发生了在材料学上被称为“缩颈”的不可逆变形,由于塑料的体积是基本恒定的,在长度增加的同时,截面积减小,袋口收缩为细绳状,从而导致与手掌的接触面积变小,压强增大,最终结果是勒得手疼.

是塑料胶带,我可以确定
以为蜡烛中含有O2(氧气),水只不过使蜡烛的所需要燃烧温度不够,用塑料带就可以隔绝水使温度达到

负电.它对金属球的负电荷排斥,金属球的负电集中到静电计的金箔上,使得金箔带的负电荷变多,从而指针偏角变大.

first we shouldnt use plastic bags when we go shopping at the supermarket