The mass of an object is a measure of the amount of matter in a body. A mountain has typically more mass than a rock, for instance. Mass should not be confused with the related but quite different concept of weight.
We can measure the mass of an object if a force acts on the object. If the mass is greater, the object will have less acceleration (change in its motion). This measure of mass is called inertial mass because it measures inertia.
A large mass like the Earth will attract a small mass like a human being with enough force to keep the human being from floating away. "Mass attraction" is another word for gravity, a force that exists between all matter. When we measure the force of gravity from an object, we can find its gravitational mass. Tests of inertial and gravitational mass show that they are the same or almost the same.
Units of mass change
The unit of mass in the International System of Units is the kilogram, which is represented by the symbol 'kg'. Fractions and multiples of this basic unit include the gram (one thousandth of a kg, symbol 'g') and the tonne (one thousand kg), amongst many others.
In some fields or applications, it is convenient to use different units to simplify the discussions or writings. For instance,
- Atomic physicists deal with the tiny masses of individual atoms and measure them in atomic mass units.
- Jewelers normally work with small jewels and precious stones where masses are traditionally measured in carats, which correspond to 200 mg or 0.2 g.
- The masses of stars are very large and are sometimes expressed in units of solar masses.
Traditional units are still in encountered in some countries: imperial units such as the ounce or the pound were in widespread use within the British Empire. Some of them are still popular in the United States, which also uses units like the short ton (2,000 pounds, 907 kg) and the long ton (2,240 pounds, 1010 kg), not to be confused with the metric ton (1,000 kg).
Conservation of mass and relativity change
Mass is an intrinsic property of the object: it does not depend on its volume, or position in space, for instance. For a long time (at least since the works of Antoine Lavoisier in the second half of the eighteen century), it has been known that the sum of the masses of objects that interact or of the chemicals that react remain conserved throughout these processes. This remains an excellent approximation for everyday life and even most laboratory work.
However, Einstein has shown through his special theory of relativity that the mass m of an object moving at speed v with respect to an observer must be higher than the mass of the same object observed at rest m0 with respect to the observer. The applicable formula is
where c stands for the speed of light. This change in mass is only important when the speed of the object with respect to the observer becomes a large fraction of c.
The Quantum Concept of Mass change
In atomic nuclei,i.e in en:Protons and en:Neutrons,the residual mass comes from the binding kinetic and potential energy of the quarks and gluon field. An analogy to go along with is to think of the 3 en:quarks as balls with the gluons as a spring connecting the quarks. This mass accounts for ~99% of the mass of these en:baryons with the remaining ~1% coming from the individual quarks which comes from quantum interactions with the Higgs field.
- Tsokos, K. A. (2005). Physics for the IB Diploma. Cambridge, United Kingdom: Cambridge University Press. p. 63. ISBN 9780521604055.
- Knight, Randall Dewey (2003). Physics for scientists and engineers with modern physics : a strategic approach. San Francisco: Pearson/Addison-Wesley. p. 349. ISBN 0-321-24329-3. OCLC 54427199.
Uzito wa kitu ni kipimo cha kiasi cha vitu katika mwili. Kwa mfano, kwa kawaida mlima huwa na uzito mkubwa kuliko mwamba. Uzito haupaswi kuchanganyikiwa na dhana inayohusiana lakini tofauti kabisa ya uzito. Tunaweza kupima wingi wa kitu ikiwa nguvu inafanya kazi kwenye kitu hicho. Ikiwa wingi ni mkubwa, kitu kitakuwa na kasi kidogo (mabadiliko katika mwendo wake). Kiwango hiki cha wingi huitwa wingi wa inertia kwa sababu hupima inertia. Kwa mfano, dunia inaweza kuvutia dunia ndogo kwa nguvu ya kutosha ili kuzuia mtu huyo asianguke. "Mvuto wa wingi" ni neno jingine la uvutano, nguvu inayopo kati ya vitu vyote. Tunapopima nguvu ya uvutano kutoka kwa kitu, tunaweza kupata uzito wake wa uvutano. Majaribio ya inertial na uzito wingi kuonyesha kwamba wao ni sawa au karibu sawa. Vipimo vya mabadiliko ya wingi Vipimo vya wingi katika Mfumo wa Kimataifa wa Vipimo ni kilo, ambayo inawakilishwa na ishara 'kg'. Fraction na multiples ya kitengo hiki msingi ni pamoja na gramu (moja elfu ya kg, ishara 'g') na tani (elfu moja kg), miongoni mwa wengine wengi. Katika baadhi ya nyanja au maombi, ni rahisi kutumia vitengo tofauti ili kurahisisha majadiliano au maandishi. Kwa mfano, - Wanafizikia wa atomu hushughulika na wingi mdogo wa atomu za mtu binafsi na kuupima katika vitengo vya wingi wa atomu. Kwa kawaida, jiwe la thamani huchukuliwa kwa karati, ambayo ni sawa na 200 mg au 0.2 g. Vipimo vya kawaida bado vinapatikana katika nchi fulani: vipimo vya kifalme kama vile unsi au paundi vilikuwa vikitumiwa sana katika Milki ya Uingereza. "Kama ilivyo kwa ""ton"" ya Marekani, ""ton"" ni kipimo cha uzito wa tani moja, na ""ton"" ni kipimo cha uzito wa tani moja, na ""ton"" ni kipimo cha uzito wa tani moja." Uhifadhi wa wingi na mabadiliko ya upendeleo Wingi ni mali ya asili ya kitu: haitegemei kiasi chake, au nafasi yake katika nafasi, kwa mfano. Tangu karne ya 18 na kazi ya Antoine Lavoisier, watu wengi walijua kwamba kiasi cha wingi wa vitu vinavyoingiliana au kemikali zinazochanganya huhifadhiwa katika mchakato huu. Hii bado ni approximation bora kwa ajili ya maisha ya kila siku na hata kazi nyingi za maabara. Einstein alionyesha katika nadharia yake ya upendeleo kwamba uzito wa kitu kinachoenda kwa kasi v kwa mtazamaji lazima uwe mkubwa kuliko uzito wa kitu hicho hicho katika hali ya kupumzika m0 kwa mtazamaji. Fomula inayotumika ni ambapo c inasimama kwa kasi ya mwanga. Mabadiliko haya ya wingi ni muhimu tu wakati kasi ya kitu kuhusiana na mtazamaji inakuwa sehemu kubwa ya c. The Quantum Concept of Mass Change Katika nyuklia za atomu, yaani katika protoni na neutroni, wingi wa mabaki hutoka kwa nguvu ya kinetic na uwezekano wa quark na uwanja wa gluon. Kwa mfano, kwa mfano, kwa mfano, kwa mfano, kwa mfano, kwa mfano, kwa mfano, kwa mfano, kwa mfano, kwa mfano, kwa mfano, kwa mfano, kwa mfano, kwa mfano, kwa mfano, kwa mfano. Kwa ujumla, uzito wa enbarion ni asilimia 99 ya uzito wa enbarion, na asilimia 1 ya uzito wa enbarion ni asilimia ya quark, ambayo hutokana na mwingiliano wa quantum na uwanja wa Higgs. - Tsokos, K. A. (2005). Fizikia kwa ajili ya IB Diploma. Cambridge, Uingereza: Cambridge Chuo Kikuu Press. P. 63 ISBN: 97821604455 - Knight, Randall Dewey (2003). Fizikia kwa wanasayansi na wahandisi na fizikia ya kisasa: mbinu ya kimkakati. San Francisco: Pearson au Addison-Wesley P. 349 ISBN 023239233 - Mfano wa Utafiti wa Utafiti OCC 542799: Mfano wa Ufafanuzi wa Ufafanuzi