求2010年中国大学生物理竞赛题目答案

2010年的是：竞赛题目（英文）
1. Electromagnetic cannon
A solenoid can be used to fire a small ball. A capacitor is used to energize the solenoid coil. Build a device with a capacitor charged to a maximum 50V. Investigate the relevant parameters and maximize the speed of the ball.
2. Brilliant pattern
Suspend a water drop at the lower end of a vertical pipe. Illuminate the drop using a laser pointer and observe the pattern created on a screen. Study and explain the structure of the pattern.
3. Steel balls
Colliding two large steel balls with a thin sheet of material (e.g. paper) in between may “burn” a hole in the sheet. Investigate this effect for various materials.
4. Soap film
Create a soap film in a circular wire loop. The soap film deforms when a charged body is placed next to it. Investigate how the shape of the soap film depends on the position and nature of the charge.
5. Grid
A plastic grid covers the open end of a cylindrical vessel containing water. The grid is covered and the vessel is turned upside down. What is the maximal size of holes in the grid so that water does not flow out when the cover is removed?
6. Ice
A wire with weights attached to each end is placed across a block of ice. The wire may pass through the ice without cutting it. Investigate the phenomenon.
7. Two flasks
Two similar flasks (one is empty, one contains water) are each connected by flexible pipes to a lower water reservoir. The flasks are heated to 100°C and this temperature is held for some time. Heating is stopped and as the flasks cool down, water is drawn up the tubes. Investigate and describe in which tube the water goes up faster and in which the final height is greater. How does this effect depend on the time of heating?
8. Liquid light guide
A transparent vessel is filled with a liquid (e.g. water). A jet flows out of the vessel. A light source is placed so that a horizontal beam enters the liquid jet (see picture). Under what conditions does the jet operate like a light guide?
9. Sticky water
When a horizontal cylinder is placed in a vertical stream of water, the stream can follow the cylinder’s circumference along the bottom and continue up the other side before it detaches. Explain this phenomenon and investigate the relevant parameters.
10. Calm surface
When wind blows across a water surface, waves can be observed. If the water is covered by an oil layer, the waves on the water surface will diminish. Investigate the phenomenon.
11. Sand
Dry sand is rather soft to walk on when compared to damp sand. However sand containing a significant amount of water becomes soft again. Investigate the parameters that affect the softness of sand.
12. Wet towels
When a wet towel is flicked, it may create a cracking sound like a whip. Investigate the effect. Why does a wet towel crack louder than a dry one?
13. Shrieking rod
A metal rod is held between two fingers and hit. Investigate how the sound produced depends on the position of holding and hitting the rod?
14. Magnetic spring
Two magnets are arranged on top of each other such that one of them is fixed and the other one can move vertically. Investigate oscillations of the magnet.
15. Paper anemometer
When thin strips of paper are placed in an air flow, a noise may be heard. Investigate how the velocity of the air flow can be deduced from this noise?
16. Rotating spring
A helical spring is rotated about one of its ends around a vertical axis. Investigate the expansion of the spring with and without an additional mass attached to its free end.
17. Kelvin’s dropper
Construct Kelvin’s dropper. Measure the highest voltage it can produce. Investigate its dependence on relevant parameters.
竞赛题目（中文）
（此版本的译文某些地方可能有出入，如果你发现有哪些地方译得不对请及时指出）
1.电磁炮
螺线管可以用来发射一个小球体。使用电容器为螺线管提供能量。以一个以50V为最大电压的电容器制作一个装置。探究球体速度的界限和如何是球体速度达到上限。
2.完美图像
一滴水悬挂在纵向水管的出口处，用一束激光去照射，观察屏上呈现的图像。研究并解释图像的结构。
3钢球
用两个巨大的钢球在一个软材料薄片（例如一张纸）处碰撞，会在这片材料上“烧”出一个洞。研究这种效应在不同材料上的体现。
4.肥皂膜
在一个圆形的水槽中制造一个肥皂膜。当把一个带电物体放在旁边时会使肥皂膜变形。探究该物体带电的方位和电性如何影响上述效应。
5.格栅
一个塑料格栅盖在一个盛有水的圆柱形容器顶部。在格栅上面盖上盖子，把容器倒置过来。在盖子移开时水不会落下来的前提下，格栅的最大孔径是多少？
6.冰块
一个两边挂有重物的金属线被横置在一个冰块上，金属线可能会自动地从冰块中穿过。探究这一现象。
7.两个烧瓶
两个相同的烧瓶（一个是空的，另一个盛有水）分别连接着一根通向一个低处蓄水池的软导管。两个烧瓶都被加热到100摄氏度并保持在此温度一段时间。当加热停止，烧瓶正在冷却时，水从导管中被吸了上去。探究在哪一个烧瓶中水会较快的被吸上去，哪一个中的水位最高。加热的时间如何影响这一效应。
8.液体导光（让光线在水流里全反射）
一个透明的圆柱形容器装满了一种液体（例如水），一束水流从容器中流出来。放置一个光源，使光束水平地射入液体流。探究在何种情况下这束水流可以像光纤一样。
9.粘稠的水
当把一个竖直的圆柱体被放置在一束竖直流下的水流之中，这束水流在掉下来之前可以沿圆柱体的圆形底面流到另一端。解释这种现象并探究相关参数。
10.平静的水面
当风吹过水面时，会产生明显的波纹，如果水面被一层油膜盖住，水面的波纹就会减小。探究这一现象。
11.沙子
相比于湿的沙子，在干燥的沙子上面行走感觉更柔软，然而，含有大量水分的沙子会重新变得柔软。探究影响沙子柔软程度的相关因素。
12.湿毛巾
如果拍动一条湿毛巾（我猜应该是用湿毛巾去抽打一个坚硬物体），会产生像用鞭子抽打一样的劈啪声。探究这一现象。为什么湿毛巾会比干毛巾发出更响亮的声音。
13.尖叫的棒子
用两个手指拿起一个铁棒，并（用某种方式）敲打它。探究手指所拿的位置和敲击的位置如何影响发出的声响。
14.磁体弹簧
两块磁体，一个放在另一个的上边。这样其中一个（下面那个）就被固定住，另一个可以竖直的移动，探究这块磁体的振动。
15.纸质风速计
当把一个薄纸条放在流动的空气中时，可能会听到一种声音。探究如何依据这种声音推断风速。
16.转动的弹簧
一个螺旋的弹簧，一端被固定着，围绕着一个竖直的轴转动，探究弹簧自由端挂重物和不挂重物时弹簧的伸长。
17.开尔文滴管
（竖直放置的磁流体发电器，开尔文滴管的具体构造最好还是去考证一下）
制造一个开尔文滴管，测量它能产生的最大电压，探究它所依赖的相关因素。