шпора по физике за первый семестр / Работа и энергия

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dWk = dA ; dA = F ds ; ds = v dt ; dA = F v dt ; F = dP/ dt ; dA = v dP ;

dWk = v dP = v d(m0 v / :>@5=L& )

@O<K< 48DD5@5=F8@>20=85< <>6=> ?>:070BL, GB>:

v d(m0 v / :>@5=L& ) = d (m0 c (AB.2)/ :>@5=L& )

dWk = d (m0 c (AB.2) / :>@5=L& ) ; P = m0 v / :>@5=L&

Wk = (m0 c (AB.2) / :>@5=L& ) + const ; ?@545;8< ?>AB>O==CN 8=B53@8@>20=8O 87 CA;>28O, GB> v = 0 ар Wk = 0 ; 0 = m0 c (AB.2) + const ар const = - m0 c (AB.2) ; Wk = (m0 c (AB.2) / :>@5=L& )  m0 c (AB.2)

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K@065=85 8<?C;LA0 G0AB8F G5@57 ?>;=CN M=5@38N:

P / m0 v = W / m0 c (AB.2) ; P = W v / c (AB.2) ;

W = m0 c (AB.2) / (:>@5=L 1  P (AB.2) c (AB.4) / W (AB.2) c(AB.2)) =

= m0 c (AB.2) W / (:>@5=L W (AB.2)  P v (AB.2)) ар W (AB.2)  P (AB.2) c (AB.2) =

= m0 (AB.2) c (AB.4) ; W = c (:>@5=L P (AB.2) + m0 v (AB.2)) ; W (AB.2) / c (AB.2)  P (AB.2) = m0 (AB.2) c (AB.2). ". :. m0, c <5=ONBAO ?@8 ?5@5E>45 >B >4=>9 8=5@F80;L=>9 A8AB5<K >BAG5B0 : 4@C3>9, B.5. O2;ONBAO 8<20@80=B=K<8 ?> >B=>H5=8N : ?@5>1@07>20=8O< >@5=F0, B> 8<20@80=B=K< 1C45B 8 >B=>H5=85: W (AB.2)  P (AB.2) = 8<20@80=B=>, B.5. ?@8 ?5@5E>45 >B >4=>9 8=5@F80;L=>9 A8AB5<K >BAG5B0 : 4@C3>9 A>E@0=O5BAO =5 >B45;L=> M=5@38O 8 >B45;L=> 8<?C;LA, 0 8<5==> MB> 2K@065=85. 7 D>@<C;K W0 = m0 c (AB.2) A;54C5B, GB> 2AO:>5 87<5=5=85 <0AAK B5;0 A>?@>2>6405BAO 87<5=5=85< M=5@388 ?>:>O delta W = delta (m c (AB.2)), >BAN40 B0:65 A;54C5B, GB> AC<<0@=0O <0AA0 2708<>459AB2CNI8E G0AB8F =5 A>E@0=O5BAO.