~急~有十點架 有關浮力的問題

1.浮力是力的一種, 指物體被放在一物體上,物體把另一物體推開,而被推開物體產生反作用力,誰浮誰沉取決於密度,低為浮,高為沉,密度取決於重量和體積, 假設把一物體於進水中, 物體體積會把水推開, 水會施反作用力,產生浮力

2. 船能浮在水面的因船的重量/體積(密度)較水低, 船的形狀是主要因素,使船體積大, 因船體積大而重量不變,所以密度低

3. 雞蛋的密度高於水,所以沉, 但加了鹽後, 水(指鹽水)的密度漸漸變高, 而雞蛋密度沒有改變,當鹽水密度高雞蛋, 雞蛋便會浮起

關於第2題,這裡有更好的解釋 http://home.sbc.edu.hk/~isc/matter.htm

由於知識有限, 請不要盡信

2009-07-27 06:30:56 補充：
不是於進是放進

1.請簡單介紹甚麼是浮力。
Upthrust (浮力) is an vetically upward force experienced by a body when it is totally or partially immersed in a fluid.
Upthrust arises due to the difference in fluid pressure at the top and bottom of the body.

2. 船為什麼能浮在水面。
According to the principle of floatation, the upthrust is equal to the weight of fluid displaced.
Ships have vast empty space in the hull. This empty space displaces quite large an amount of water, thus increasing the upthrust. When the upthrust balances the weight of the ship, the ship floats.

3. 假如在一杯水中放入一只雞蛋，為什麼在加入適量的鹽後，能使雞蛋浮在水面。
The adding of salt increases the magnitude of upthrust on a body.
Salt water has a larger densith than pure water. Thus, for a fixed volume of water displaced, the weight of salt water weights more than pure water. That is to say, the upthrust (which equals to the weight of water dispalced) becomes larger, and which is sufficient to float the egg.