Galileo experiment

Physics: Galileo’s pendulum?
Galileo experiment

1.點解from the result of the 'pin and pendulum' experiment Galileo argued that the ball bearing in the thought experiment would rise to the same height?

In his 'pin and pendulum' experiment Galileo also noted that a pendulum's swings always take the same amount of time, independently of the amplitude, in fact that could be visualized as its energy input is equal to its energy output.

2. The ball bearing in the thought experiment would rise to the same height 代表左D 咩?

Galileo determined the correct mathematical law for acceleration: the total distance covered, starting from rest, is proportional to the square of the time (). He expressed this law using geometrical constructions and mathematically-precise words, adhering to the standards of the day. (It remained for others to re-express the law in algebraic terms). He also concluded that objects retain their velocity unless a force—often friction—acts upon them, refuting the generally accepted Aristotelian hypothesis that objects "naturally" slow down and stop unless a force acts upon them (again this was not a new idea: Ibn al-Haytham had proposed it centuries earlier, as had Jean Buridan, and according to Joseph Needham, Mo Tzu had proposed it centuries before either of them, but this was the first time that it had been mathematically expressed). Galileo's Principle of Inertia stated: "A body moving on a level surface will continue in the same direction at constant speed unless the moving body had disturbed by an external forces, one of the examples is the force of gravitation acceleration of the planet, just like the gravitation acceleration that we are experiencing on our planet Earth."

Online reference: http://en.wikipedia.org/wiki/Galileo#Scientific_methods

3. 從這experiment 那裏可以看到it is natural for a moving body to move at a constant speed along a straight line and natural for a stationary object to remain at rest?

Galileo also noted that a pendulum's swings always take the same amount of time, independently of the amplitude. The story goes that he came to this conclusion by watching the swings of the bronze chandelier in the cathedral of Pisa, using his pulse to time it. While Galileo believed this equality of period to be exact, it is only an approximation appropriate to small amplitudes. It is good enough to regulate a pendulum clock, however, as Galileo may have been the first to realize.

Galileo proved, with a virtuoso display of Greek geometry, that the fact that the vertical drop was proportional to the square of the horizontal distance meant that the trajectory was a parabola. His definition of a parabola, the classic Greek definition, was that it was the intersection of a cone with a plane parallel to one side of the cone. Starting from this definition of a parabola, it takes quite a lot of work to establish that the trajectory is parabolic. However, if we define a parabola as a curve of the form y =Cx² then of course we've proved it already!

online reference: http://galileo.phys.virginia.edu/classes/109N/lectures/gal_accn962.htm

2007-12-17 13:19:07 補充：
3 b. In fact, that could also be explain by Newton's First Law states that an object will remain at rest or in uniform motion in a straight line unless acted upon by an external force.