大學(xué)物理演示實(shí)驗(yàn)英文版

1、Build a Raft Powered by Surface Tension AbstractHave you ever wondered why a water strider can walk on water? Or how detergent can clean your dishes? If you observe carefully, you can find dozens of similarly interesting

2、 phenomena that are all linked to the surface tension of water. This science project will help you understand and measure the properties of water surface tension. ObjectiveIn this science project, you will: 1. Develop an

3、 understanding of water surface tension, 2. Understand changes in water surface tension under various conditions, 3. Make measurements to estimate the net water surface tension. IntroductionIf you've ever blown up a

4、balloon, you know it's pretty easy to blow up without becoming out of breath when it's made of soft, stretchy rubber. That's because the balloon offers little resistanceto becoming stretched out as it is blow

5、n up. But for a balloon made of thicker or stiffer rubber, more energy is required to blow it up. The balloon offers more resistance to stretching. Think of a balloon as a model for surface tension. How “stretchy“ the ba

6、lloon material is determines how much resistance (surface tension) must be overcome by the energy of your blowing in order to inflate the balloon. Surface tensionis defined as the energy required to increase the surface

7、 area by a unit amount. Liquids also experience surface tension. The molecules(small individual particles) of the liquid experience intermolecular attractions, which simply means the molecules are pulling and pushing aw

8、ay from each other, just like magnets both attract and repel each other. In the case of a water molecule surrounded on all sides by other water molecules, every pulling force is balanced by a pushing force. The net (whic

9、h means overall ) effect is no change. But at the surface, where air and water meet, that isn't true. The water molecules at the surface experience more pulls downward toward the other water molecules below them tha

10、n upward toward the air. This is the surface tension of the water. You can see it at work when you fill a glass. Even if the water is at the rim of the glass, you can add just a few more drops so that the water is slight

11、ly taller than the rim. Don't believe it? Look at the picture below and then try it yourself! Exploratorium. (n.d.). Sticky Water.Retrieved August 12, 2010, from http://www.exploratorium.edu/ronh/bubbles/sticky_wate

12、r.htmlThis website offers an explanation of velocity:Physics4Kids. (n.d.). Velocity, Speed, and Motion...Oh My!Retrieved August 12, 2010, from http://www.physics4kids.com/files/motion_velocity.htmlThis website explain

13、s kinetic energy:Zobel, E.A. (n.d.). Kinetic Energy.Retrieved August 12, 2010, from http://zonalandeducation.com/mstm/physics/mechanics/energy/kineticEnergy/kineticEnergy.htmlMaterials and EquipmentTransparencies, like

14、 those used on an overhead projector (1 box); available at your local office supply store Marker Ruler, metric Scissors Kitchen sponges (1 package) Tape Lab notebook Liquid laundry detergent Eye dropper; available at you

15、r local pharmacy Stopwatch, accurate to 0.01 second (sec) Scale, one that can detect small masses in grams (g). A good kitchen scale will work. Alternatively, try a postal scale. You might be able to use the one at your

16、local post office, or your school might have a triple-beam balance. Liquid hand soap Toothpaste Toothpicks (1 box) Water Large basin or sink to hold the water and your transparency raft in early trials o It should be lar