Some question about phy

我想問吓係唔係所有物質都有重量(包括光子,wave , etc)?

No. Energy does not possess any mass. Photons or waves thus have no (rest) mass.

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i would want to ask is there any energy inside the substance when it is at rest?

Yes. There are binding energy between particles inside a substance in the microscopic scale. Macroscopically, atoms or molecules in a substance are continuously vibrating, and for gases, there are random translational motion of their molecules.

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will the mass of an object change when it is traveling ?

Special relativity tells that the mass of a substance appears to increase when the speed of the mass increases.

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* there is only force in the substance when there is energy supplied

if the above sentence is correct , is there any energy supplied to the earth so

that it can be moved ?

The present rotation and revoluton of the earth does not require any further input of energy. The motions are entirely due to inertia. Should energy be supplied to the earth, we would expect that the time for one full day becomes shorter and shorter (due to increase of rotational speed) and the seasonal change be more rapid (due to increase in revolution speed).

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E=mc2 is mean what?

It is the mass-energy equivalence relation in Special Relativity. It gives the energy equivalence of mass (i.e. to how to measure mass in energy terms)

Notice that this equation does not imply that energy possesses mass. Do not wrongly interprete it.

2008-05-24 01:19:17 補充：

the time will be stopped when something reached the speed of the light.

am i correct?

It should be interprete as the time of a traveller would come to a stand still when viewed from another inertia reference system that has a speed equal to the speed of light.

2008-05-24 01:19:56 補充：

The traveller himself would feel that time passes in the usual pace.

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what will be the situation if something travel faster than speed of light?

2008-05-24 01:20:28 補充：

Present physics knowledge could not tell what would happen in situation that light speed is exceeded. All laws of physics fail under such situation.