Sila – razlika između verzija
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Red 127:
Dakako, ne može se isključiti mogućnost postojanja i drugih vrsta sila koje ljudi još nisu opazili, i pored visokog stupnja suglasnosti oko fizikalnih modela koji se oslanjaju na četiri navedene interakcije. Neke alternativne ili hipotetičke opcije pod nazivom '''peta sila''' spominju se u posljednje vrijeme u različitim kontekstima, npr. tumačenja tamne energije, ili istraživanja sudara ubrzanih čestica.<ref>Fermilab Today, 12. 05. 2011.</ref>
== Kinematički integrali ==
{{main|Impuls sile|l1=Impuls|Mehanički rad|Snaga}}
Sile se mogu koristiti za definisanje brojnih fizičkih koncepta putem [[integral|integracije]] po [[kinematika|kinematičkim promenljivama]]. For example, integrating with respect to time gives the definition of [[Impulse (physics)|impulse]]:<ref>{{Cite book
|title=Engineering Mechanics, 12th edition
|first1=Russell C.
|last1=Hibbeler
|publisher=Pearson Prentice Hall
|year=2010
|isbn=0-13-607791-9
|page=222
|postscript=<!--None-->}}</ref>
:<math>\vec{I}=\int_{t_1}^{t_2}{\vec{F} \mathrm{d}t},</math>
which by Newton's Second Law must be equivalent to the change in momentum (yielding the [[Impulse momentum theorem]]).
Similarly, integrating with respect to position gives a definition for the [[work (physics)|work done]] by a force:<ref name=FeynmanVol1/>{{rp|13-3}}
:<math>W=\int_{\vec{x}_1}^{\vec{x}_2}{\vec{F} \cdot{\mathrm{d}\vec{x}}},</math>
which is equivalent to changes in [[kinetic energy]] (yielding the [[work energy theorem]]).<ref name=FeynmanVol1/>{{rp|13-3}}
[[Power (physics)|Power]] ''P'' is the rate of change d''W''/d''t'' of the work ''W'', as the [[trajectory]] is extended by a position change <math>\scriptstyle {d}\vec{x}</math> in a time interval d''t'':<ref name=FeynmanVol1/>{{rp|13-2}}
:<math>
\text{d}W\, =\, \frac{\text{d}W}{\text{d}\vec{x}}\, \cdot\, \text{d}\vec{x}\, =\, \vec{F}\, \cdot\, \text{d}\vec{x},
\qquad \text{ so } \quad
P\, =\, \frac{\text{d}W}{\text{d}t}\, =\, \frac{\text{d}W}{\text{d}\vec{x}}\, \cdot\, \frac{\text{d}\vec{x}}{\text{d}t}\, =\, \vec{F}\, \cdot\, \vec{v},
</math>
with <math>{\vec{v}\text{ }=\text{ d}\vec{x}/\text{d}t}</math> the [[velocity]].
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